diff --git a/src/broker/log.c b/src/broker/log.c
index e456cef82a92..1046bd8b8747 100644
--- a/src/broker/log.c
+++ b/src/broker/log.c
@@ -481,7 +481,7 @@ static void append_request_cb (flux_t *h, flux_msg_handler_t *mh,
     logbuf_t *logbuf = arg;
     uint32_t matchtag;
     const char *buf;
-    int len;
+    size_t len;
 
     if (flux_msg_get_matchtag (msg, &matchtag) < 0) {
         log_msg ("%s: malformed log request", __FUNCTION__);
diff --git a/src/broker/trace.c b/src/broker/trace.c
index b15f7f892ec8..aabca09655b1 100644
--- a/src/broker/trace.c
+++ b/src/broker/trace.c
@@ -54,7 +54,7 @@ static void trace_msg (flux_t *h,
     int type = 0;
     char buf[64];
     const char *topic = NULL;
-    int payload_size = 0;
+    size_t payload_size = 0;
     json_t *payload_json = NULL;
     int errnum = 0;
     const char *errstr = NULL;
diff --git a/src/cmd/builtin/content.c b/src/cmd/builtin/content.c
index ce54c0751526..237e1e8f1fcc 100644
--- a/src/cmd/builtin/content.c
+++ b/src/cmd/builtin/content.c
@@ -23,7 +23,7 @@ static void load_to_fd (flux_t *h, int fd, const char *blobref, int flags)
 {
     flux_future_t *f;
     const uint8_t *data;
-    int size;
+    size_t size;
 
     if (!(f = content_load_byblobref (h, blobref, flags))
         || content_load_get (f, (const void **)&data, &size) < 0)
diff --git a/src/cmd/builtin/dump.c b/src/cmd/builtin/dump.c
index 00d569533bc3..9266abe0b7f5 100644
--- a/src/cmd/builtin/dump.c
+++ b/src/cmd/builtin/dump.c
@@ -154,7 +154,7 @@ static void dump_valref (struct archive *ar,
     int total_size = 0;
     struct archive_entry *entry;
     const void *data;
-    int len;
+    size_t len;
 
     /* We need the total size before we start writing archive data,
      * so make a first pass, saving the data for writing later.
@@ -220,7 +220,7 @@ static void dump_val (struct archive *ar,
 {
     struct archive_entry *entry;
     void *data;
-    int len;
+    size_t len;
 
     if (treeobj_decode_val (treeobj, &data, &len) < 0)
         log_err_exit ("%s: invalid value object", path);
@@ -296,7 +296,7 @@ static void dump_dirref (struct archive *ar,
 {
     flux_future_t *f;
     const void *buf;
-    int buflen;
+    size_t buflen;
     json_t *treeobj_deref = NULL;
 
     if (treeobj_get_count (treeobj) != 1)
@@ -356,7 +356,7 @@ static void dump_blobref (struct archive *ar,
 {
     flux_future_t *f;
     const void *buf;
-    int buflen;
+    size_t buflen;
     json_t *treeobj;
     json_t *dict;
     const char *key;
diff --git a/src/cmd/flux-event.c b/src/cmd/flux-event.c
index b6184b632efa..7fa924635716 100644
--- a/src/cmd/flux-event.c
+++ b/src/cmd/flux-event.c
@@ -256,7 +256,7 @@ static int event_pub (optparse_t *p, int argc, char **argv)
                 log_err_exit ("flux_recv error");
             if (optparse_hasopt (p, "raw")) {
                 const void *data;
-                int len;
+                size_t len;
                 if ((flux_event_decode_raw (msg, NULL, &data, &len) == 0
                     && match_payload_raw (payload, payloadsz, data, len)))
                     received = true;
@@ -350,7 +350,7 @@ static void event_cb (flux_t *h,
     int max_count = optparse_get_int (p, "count", 0);
     static int recv_count = 0;
     const char *payload;
-    int payloadsz;
+    size_t payloadsz;
     const char *topic;
 
     if (flux_event_decode (msg, &topic, &payload) == 0)
diff --git a/src/cmd/flux-kvs.c b/src/cmd/flux-kvs.c
index b887cf47c9b4..1235ded9abab 100644
--- a/src/cmd/flux-kvs.c
+++ b/src/cmd/flux-kvs.c
@@ -712,7 +712,7 @@ void lookup_continuation (flux_future_t *f, void *arg)
     }
     else if (optparse_hasopt (ctx->p, "raw")) {
         const void *data;
-        int len;
+        size_t len;
         if (flux_kvs_lookup_get_raw (f, &data, &len) < 0)
             log_err_exit ("%s", key);
         if (optparse_hasopt (ctx->p, "label"))
@@ -1291,7 +1291,7 @@ static void dump_kvs_dir (const flux_kvsdir_t *dir, int maxcol,
             if (!dopt) {
                 const char *value;
                 const void *buf;
-                int len;
+                size_t len;
                 if (rootref) {
                     if (!(f = flux_kvs_lookupat (h, 0, key, rootref)))
                         log_err_exit ("%s", key);
@@ -1303,7 +1303,7 @@ static void dump_kvs_dir (const flux_kvsdir_t *dir, int maxcol,
                 if (flux_kvs_lookup_get (f, &value) == 0) // null terminated
                     dump_kvs_val (key, maxcol, value);
                 else if (flux_kvs_lookup_get_raw  (f, &buf, &len) == 0)
-                    kv_printf (key, maxcol, "%.*s", len, (char *)buf);
+                    kv_printf (key, maxcol, "%.*s", (int)len, (char *)buf);
                 else
                     log_err_exit ("%s", key);
                 flux_future_destroy (f);
diff --git a/src/common/libcontent/content.c b/src/common/libcontent/content.c
index 865aaff57e3c..196ac67f2c42 100644
--- a/src/common/libcontent/content.c
+++ b/src/common/libcontent/content.c
@@ -23,7 +23,7 @@
 
 flux_future_t *content_load_byhash (flux_t *h,
                                     const void *hash,
-                                    int hash_size,
+                                    size_t hash_size,
                                     int flags)
 {
     const char *topic = "content.load";
@@ -47,19 +47,19 @@ flux_future_t *content_load_byblobref (flux_t *h,
                                        int flags)
 {
     uint32_t hash[BLOBREF_MAX_DIGEST_SIZE];
-    int hash_size;
+    ssize_t hash_size;
 
     if ((hash_size = blobref_strtohash (blobref, hash, sizeof (hash))) < 0)
         return NULL;
     return content_load_byhash (h, hash, hash_size, flags);
 }
 
-int content_load_get (flux_future_t *f, const void **buf, int *len)
+int content_load_get (flux_future_t *f, const void **buf, size_t *len)
 {
     return flux_rpc_get_raw (f, buf, len);
 }
 
-flux_future_t *content_store (flux_t *h, const void *buf, int len, int flags)
+flux_future_t *content_store (flux_t *h, const void *buf, size_t len, int flags)
 {
     const char *topic = "content.store";
     uint32_t rank = FLUX_NODEID_ANY;
@@ -73,10 +73,12 @@ flux_future_t *content_store (flux_t *h, const void *buf, int len, int flags)
     return flux_rpc_raw (h, topic, buf, len, rank, 0);
 }
 
-int content_store_get_hash (flux_future_t *f, const void **hash, int *hash_size)
+int content_store_get_hash (flux_future_t *f,
+                            const void **hash,
+                            size_t *hash_size)
 {
     const void *buf;
-    int buf_size;
+    size_t buf_size;
 
     if (flux_rpc_get_raw (f, &buf, &buf_size) < 0)
         return -1;
@@ -96,7 +98,7 @@ int content_store_get_blobref (flux_future_t *f,
 
     if (!(result = flux_future_aux_get (f, auxkey))) {
         const void *hash;
-        int hash_len;
+        size_t hash_len;
         char buf[BLOBREF_MAX_STRING_SIZE];
         char *cpy = NULL;
 
diff --git a/src/common/libcontent/content.h b/src/common/libcontent/content.h
index d97d697b4b97..6d31ff04f98f 100644
--- a/src/common/libcontent/content.h
+++ b/src/common/libcontent/content.h
@@ -21,7 +21,7 @@ enum {
  */
 flux_future_t *content_load_byhash (flux_t *h,
                                     const void *hash,
-                                    int hash_len,
+                                    size_t hash_len,
                                     int flags);
 flux_future_t *content_load_byblobref (flux_t *h,
                                        const char *blobref,
@@ -32,17 +32,22 @@ flux_future_t *content_load_byblobref (flux_t *h,
  * Storage for 'buf' belongs to 'f' and is valid until 'f' is destroyed.
  * Returns 0 on success, -1 on failure with errno set.
  */
-int content_load_get (flux_future_t *f, const void **buf, int *len);
+int content_load_get (flux_future_t *f, const void **buf, size_t *len);
 
 /* Send request to store blob.
  */
-flux_future_t *content_store (flux_t *h, const void *buf, int len, int flags);
+flux_future_t *content_store (flux_t *h,
+                              const void *buf,
+                              size_t len,
+                              int flags);
 
 /* Get result of store request (hash or blobref).
  * Storage belongs to 'f' and is valid until 'f' is destroyed.
  * Returns 0 on success, -1 on failure with errno set.
  */
-int content_store_get_hash (flux_future_t *f, const void **hash, int *hash_len);
+int content_store_get_hash (flux_future_t *f,
+                            const void **hash,
+                            size_t *hash_len);
 int content_store_get_blobref (flux_future_t *f,
                                const char *hash_name,
                                const char **blobref);
diff --git a/src/common/libfilemap/filemap.c b/src/common/libfilemap/filemap.c
index cba352f99f59..a7395143336f 100644
--- a/src/common/libfilemap/filemap.c
+++ b/src/common/libfilemap/filemap.c
@@ -82,7 +82,7 @@ static int extract_blob (flux_t *h,
     } entry;
     flux_future_t *f;
     const void *buf;
-    int size;
+    size_t size;
 
     if (json_unpack (o,
                      "[I,I,s]",
diff --git a/src/common/libflux/event.c b/src/common/libflux/event.c
index 2d2df9146769..f56d187da1ed 100644
--- a/src/common/libflux/event.c
+++ b/src/common/libflux/event.c
@@ -130,11 +130,11 @@ int flux_event_decode (const flux_msg_t *msg,
 int flux_event_decode_raw (const flux_msg_t *msg,
                            const char **topicp,
                            const void **datap,
-                           int *lenp)
+                           size_t *lenp)
 {
     const char *topic;
     const void *data = NULL;
-    int len = 0;
+    size_t len = 0;
     int rc = -1;
 
     if (!datap || !lenp) {
@@ -224,7 +224,7 @@ flux_msg_t *flux_event_encode (const char *topic, const char *s)
 
 flux_msg_t *flux_event_encode_raw (const char *topic,
                                    const void *data,
-                                   int len)
+                                   size_t len)
 {
     flux_msg_t *msg = flux_event_create (topic);
     if (!msg)
@@ -267,7 +267,7 @@ static flux_future_t *wrap_event_rpc (flux_t *h,
                                       const char *topic,
                                       int flags,
                                       const void *src,
-                                      int srclen)
+                                      size_t srclen)
 {
     flux_future_t *f;
 
@@ -371,7 +371,7 @@ flux_future_t *flux_event_publish_raw (flux_t *h,
                                        const char *topic,
                                        int flags,
                                        const void *data,
-                                       int len)
+                                       size_t len)
 {
     if (!h || !topic || (flags & ~(FLUX_MSGFLAG_PRIVATE)) != 0) {
         errno = EINVAL;
diff --git a/src/common/libflux/event.h b/src/common/libflux/event.h
index 5cc8b5e4724a..1848a811de19 100644
--- a/src/common/libflux/event.h
+++ b/src/common/libflux/event.h
@@ -63,7 +63,7 @@ flux_msg_t *flux_event_pack (const char *topic, const char *fmt, ...);
  */
 flux_msg_t *flux_event_encode_raw (const char *topic,
                                    const void *data,
-                                   int len);
+                                   size_t len);
 
 /* Decode an event message, with optional raw payload.
  * If topic is non-NULL, assign the event topic string.
@@ -74,7 +74,7 @@ flux_msg_t *flux_event_encode_raw (const char *topic,
 int flux_event_decode_raw (const flux_msg_t *msg,
                            const char **topic,
                            const void **data,
-                           int *len);
+                           size_t *len);
 
 /* Publish an event with optional string payload.
  * The future is fulfilled once the event has been assigned a sequence number,
@@ -99,7 +99,7 @@ flux_future_t *flux_event_publish_raw (flux_t *h,
                                        const char *topic,
                                        int flags,
                                        const void *data,
-                                       int len);
+                                       size_t len);
 
 /* Obtain the event sequence number from the fulfilled
  * flux_event_publish() future.
diff --git a/src/common/libflux/message.c b/src/common/libflux/message.c
index cdf1d9af01bd..e34870527d4f 100644
--- a/src/common/libflux/message.c
+++ b/src/common/libflux/message.c
@@ -842,7 +842,7 @@ static bool payload_overlap (flux_msg_t *msg, const void *b)
          && (char *)b <  (char *)msg->payload + msg->payload_size);
 }
 
-int flux_msg_set_payload (flux_msg_t *msg, const void *buf, int size)
+int flux_msg_set_payload (flux_msg_t *msg, const void *buf, size_t size)
 {
     if (msg_validate (msg) < 0)
         return -1;
@@ -968,7 +968,7 @@ int flux_msg_pack (flux_msg_t *msg, const char *fmt, ...)
     return rc;
 }
 
-int flux_msg_get_payload (const flux_msg_t *msg, const void **buf, int *size)
+int flux_msg_get_payload (const flux_msg_t *msg, const void **buf, size_t *size)
 {
     if (msg_validate (msg) < 0)
         return -1;
@@ -1003,7 +1003,7 @@ int flux_msg_get_string (const flux_msg_t *msg, const char **s)
 {
     const char *buf;
     const char *result;
-    int size;
+    size_t size;
 
     if (msg_validate (msg) < 0)
         return -1;
@@ -1366,7 +1366,7 @@ void flux_msg_fprint_ts (FILE *f, const flux_msg_t *msg, double timestamp)
     if (flux_msg_has_payload (msg)) {
         const char *s;
         const void *buf;
-        int size;
+        size_t size;
         if (flux_msg_get_string (msg, &s) == 0)
             fprintf (f, "%s %s\n", prefix, s);
         else if (flux_msg_get_payload (msg, &buf, &size) == 0) {
diff --git a/src/common/libflux/message.h b/src/common/libflux/message.h
index 57f0a7ff2b76..94fab74a6bb9 100644
--- a/src/common/libflux/message.h
+++ b/src/common/libflux/message.h
@@ -166,8 +166,10 @@ int flux_msg_get_topic (const flux_msg_t *msg, const char **topic);
  * Any old payload is deleted.
  * flux_msg_get_payload returns pointer to msg-owned buf.
  */
-int flux_msg_get_payload (const flux_msg_t *msg, const void **buf, int *size);
-int flux_msg_set_payload (flux_msg_t *msg, const void *buf, int size);
+int flux_msg_get_payload (const flux_msg_t *msg,
+                          const void **buf,
+                          size_t *size);
+int flux_msg_set_payload (flux_msg_t *msg, const void *buf, size_t size);
 bool flux_msg_has_payload (const flux_msg_t *msg);
 
 /* Test/set/clear message flags
diff --git a/src/common/libflux/request.c b/src/common/libflux/request.c
index a20c640498e2..d42f09d8e562 100644
--- a/src/common/libflux/request.c
+++ b/src/common/libflux/request.c
@@ -63,11 +63,11 @@ int flux_request_decode (const flux_msg_t *msg,
 int flux_request_decode_raw (const flux_msg_t *msg,
                              const char **topic,
                              const void **data,
-                             int *len)
+                             size_t *len)
 {
     const char *ts;
     const void *d = NULL;
-    int l = 0;
+    size_t l = 0;
     int rc = -1;
 
     if (!data || !len) {
@@ -162,7 +162,7 @@ flux_msg_t *flux_request_encode (const char *topic, const char *s)
 
 flux_msg_t *flux_request_encode_raw (const char *topic,
                                      const void *data,
-                                     int len)
+                                     size_t len)
 {
     flux_msg_t *msg = request_encode (topic);
 
diff --git a/src/common/libflux/request.h b/src/common/libflux/request.h
index cabfee85dfa3..b460fdee9d17 100644
--- a/src/common/libflux/request.h
+++ b/src/common/libflux/request.h
@@ -42,7 +42,7 @@ int flux_request_unpack (const flux_msg_t *msg,
 int flux_request_decode_raw (const flux_msg_t *msg,
                              const char **topic,
                              const void **data,
-                             int *len);
+                             size_t *len);
 
 /* Encode a request message with optional string payload.
  * If s is non-NULL, assign the string payload.
@@ -55,7 +55,7 @@ flux_msg_t *flux_request_encode (const char *topic, const char *s);
  */
 flux_msg_t *flux_request_encode_raw (const char *topic,
                                      const void *data,
-                                     int len);
+                                     size_t len);
 
 #ifdef __cplusplus
 }
diff --git a/src/common/libflux/response.c b/src/common/libflux/response.c
index 2404a9433c08..cef0718eadf1 100644
--- a/src/common/libflux/response.c
+++ b/src/common/libflux/response.c
@@ -71,11 +71,11 @@ int flux_response_decode (const flux_msg_t *msg,
 int flux_response_decode_raw (const flux_msg_t *msg,
                               const char **topic,
                               const void **data,
-                              int *len)
+                              size_t *len)
 {
     const char *ts;
     const void *d = NULL;
-    int l = 0;
+    size_t l = 0;
     int rc = -1;
 
     if (!data || !len) {
@@ -167,7 +167,7 @@ flux_msg_t *flux_response_encode (const char *topic, const char *s)
 
 flux_msg_t *flux_response_encode_raw (const char *topic,
                                       const void *data,
-                                      int len)
+                                      size_t len)
 {
     flux_msg_t *msg;
 
diff --git a/src/common/libflux/response.h b/src/common/libflux/response.h
index 5ad456f079ce..d06839d8d8a9 100644
--- a/src/common/libflux/response.h
+++ b/src/common/libflux/response.h
@@ -38,7 +38,7 @@ int flux_response_decode (const flux_msg_t *msg,
 int flux_response_decode_raw (const flux_msg_t *msg,
                               const char **topic,
                               const void **data,
-                              int *len);
+                              size_t *len);
 
 /* If failed response includes an error string payload, assign to 'errstr',
  * otherwise fail.
@@ -55,7 +55,7 @@ flux_msg_t *flux_response_encode (const char *topic, const char *s);
  */
 flux_msg_t *flux_response_encode_raw (const char *topic,
                                       const void *data,
-                                      int len);
+                                      size_t len);
 
 /* Encode an error response with 'errnum' (must be nonzero) and
  * if non-NULL, an error string payload.
diff --git a/src/common/libflux/rpc.c b/src/common/libflux/rpc.c
index 657ed524e22e..74917c371723 100644
--- a/src/common/libflux/rpc.c
+++ b/src/common/libflux/rpc.c
@@ -123,7 +123,7 @@ int flux_rpc_get (flux_future_t *f, const char **s)
     return rc;
 }
 
-int flux_rpc_get_raw (flux_future_t *f, const void **data, int *len)
+int flux_rpc_get_raw (flux_future_t *f, const void **data, size_t *len)
 {
     const flux_msg_t *msg;
     int rc = -1;
@@ -331,7 +331,7 @@ flux_future_t *flux_rpc (flux_t *h,
 flux_future_t *flux_rpc_raw (flux_t *h,
                              const char *topic,
                              const void *data,
-                             int len,
+                             size_t len,
                              uint32_t nodeid,
                              int flags)
 {
diff --git a/src/common/libflux/rpc.h b/src/common/libflux/rpc.h
index 78ff2d855359..667f56d13972 100644
--- a/src/common/libflux/rpc.h
+++ b/src/common/libflux/rpc.h
@@ -43,7 +43,7 @@ flux_future_t *flux_rpc_vpack (flux_t *h,
 flux_future_t *flux_rpc_raw (flux_t *h,
                              const char *topic,
                              const void *data,
-                             int len,
+                             size_t len,
                              uint32_t nodeid,
                              int flags);
 
@@ -56,7 +56,7 @@ int flux_rpc_get (flux_future_t *f, const char **s);
 
 int flux_rpc_get_unpack (flux_future_t *f, const char *fmt, ...);
 
-int flux_rpc_get_raw (flux_future_t *f, const void **data, int *len);
+int flux_rpc_get_raw (flux_future_t *f, const void **data, size_t *len);
 
 /* Accessor for RPC matchtag (see RFC 6).
  */
diff --git a/src/common/libflux/test/event.c b/src/common/libflux/test/event.c
index 192800b165e2..6aa6fea5d541 100644
--- a/src/common/libflux/test/event.c
+++ b/src/common/libflux/test/event.c
@@ -25,8 +25,8 @@ void test_codec (void)
     const char data[] = "bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb";
     int len = strlen (data);
     const void *d;
-    int l;
-    int i;
+    size_t l;
+    size_t i;
 
     /* no topic is an error */
     errno = 0;
diff --git a/src/common/libflux/test/message.c b/src/common/libflux/test/message.c
index 9abf9f864666..0ec8d18bc975 100644
--- a/src/common/libflux/test/message.c
+++ b/src/common/libflux/test/message.c
@@ -39,7 +39,7 @@ void check_cornercase (void)
     uint32_t tag;
     const char *topic;
     const void *payload;
-    int payload_size;
+    size_t payload_size;
 
     errno = 0;
     ok (flux_msg_create (0xFFFF) == NULL && errno == EINVAL,
@@ -634,7 +634,8 @@ void check_payload (void)
     flux_msg_t *msg;
     const void *buf;
     void *pay[1024];
-    int plen = sizeof (pay), len;
+    size_t plen = sizeof (pay);
+    size_t len;
 
     ok ((msg = flux_msg_create (FLUX_MSGTYPE_REQUEST)) != NULL,
        "flux_msg_create works");
@@ -995,7 +996,7 @@ void check_copy (void)
     flux_msg_t *msg, *cpy;
     int type;
     const char *topic;
-    int cpylen;
+    size_t cpylen;
     const char buf[] = "xxxxxxxxxxxxxxxxxx";
     const void *cpybuf;
     const char *s;
diff --git a/src/common/libflux/test/request.c b/src/common/libflux/test/request.c
index a3ffc6642a07..35452f81c9c7 100644
--- a/src/common/libflux/test/request.c
+++ b/src/common/libflux/test/request.c
@@ -25,7 +25,9 @@ int main (int argc, char *argv[])
     const char *json_str = "{\"a\":42}";
     const void *d;
     const char data[] = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
-    int i, l, len = strlen (data);
+    size_t i;
+    size_t l;
+    size_t len = strlen (data);
 
     plan (NO_PLAN);
 
diff --git a/src/common/libflux/test/response.c b/src/common/libflux/test/response.c
index 2aaf5e436ff8..6128c270cfff 100644
--- a/src/common/libflux/test/response.c
+++ b/src/common/libflux/test/response.c
@@ -27,7 +27,8 @@ int main (int argc, char *argv[])
     const char *json_str = "{\"a\":42}";
     const void *d;
     const char data[] = "bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb";
-    int l, len = strlen (data);
+    size_t l;
+    size_t len = strlen (data);
     int errnum;
 
     plan (NO_PLAN);
diff --git a/src/common/libflux/test/rpc.c b/src/common/libflux/test/rpc.c
index 4dbc2a82a6c4..4b6c783cb404 100644
--- a/src/common/libflux/test/rpc.c
+++ b/src/common/libflux/test/rpc.c
@@ -124,7 +124,7 @@ void rpctest_rawecho_cb (flux_t *h,
                          void *arg)
 {
     const void *d = NULL;
-    int l = 0;
+    size_t l = 0;
 
     if (flux_request_decode_raw (msg, NULL, &d, &l) < 0)
         goto error;
@@ -494,7 +494,7 @@ void test_encoding (flux_t *h)
     /* working with-payload RPC (raw) */
     const void *d;
     const char data[] = "aaaaaaaaaaaaaaaaaaaa";
-    int l, len = strlen (data);
+    size_t l, len = strlen (data);
     ok ((r = flux_rpc_raw (h,
                            "rpctest.rawecho",
                            data,
diff --git a/src/common/libflux/test/rpcscale.c b/src/common/libflux/test/rpcscale.c
index 8814e44cb7fa..7048dc4e5ac3 100644
--- a/src/common/libflux/test/rpcscale.c
+++ b/src/common/libflux/test/rpcscale.c
@@ -29,7 +29,7 @@ void ping_cb (flux_t *h,
               void *arg)
 {
     const void *payload;
-    int payload_len;
+    size_t payload_len;
 
     if (flux_request_decode_raw (msg, NULL, &payload, &payload_len) < 0)
         goto error;
diff --git a/src/common/libkvs/kvs_lookup.c b/src/common/libkvs/kvs_lookup.c
index e2783c80f970..716fb6f7dc4c 100644
--- a/src/common/libkvs/kvs_lookup.c
+++ b/src/common/libkvs/kvs_lookup.c
@@ -31,7 +31,7 @@ struct lookup_ctx {
     json_t *treeobj;
     char *treeobj_str; // json_dumps of tree object returned from lookup
     void *val_data;    // result of base64 decode of val object data
-    int val_len;
+    size_t val_len;
     bool val_valid;
     json_t *val_obj;
     flux_kvsdir_t *dir;
@@ -333,7 +333,7 @@ int flux_kvs_lookup_get_unpack (flux_future_t *f, const char *fmt, ...)
     return rc;
 }
 
-int flux_kvs_lookup_get_raw (flux_future_t *f, const void **data, int *len)
+int flux_kvs_lookup_get_raw (flux_future_t *f, const void **data, size_t *len)
 {
     struct lookup_ctx *ctx;
 
diff --git a/src/common/libkvs/kvs_lookup.h b/src/common/libkvs/kvs_lookup.h
index e2f3b2d5bba0..d3a7717ec89a 100644
--- a/src/common/libkvs/kvs_lookup.h
+++ b/src/common/libkvs/kvs_lookup.h
@@ -26,7 +26,7 @@ flux_future_t *flux_kvs_lookupat (flux_t *h,
 
 int flux_kvs_lookup_get (flux_future_t *f, const char **value);
 int flux_kvs_lookup_get_unpack (flux_future_t *f, const char *fmt, ...);
-int flux_kvs_lookup_get_raw (flux_future_t *f, const void **data, int *len);
+int flux_kvs_lookup_get_raw (flux_future_t *f, const void **data, size_t *len);
 int flux_kvs_lookup_get_treeobj (flux_future_t *f, const char **treeobj);
 int flux_kvs_lookup_get_dir (flux_future_t *f, const flux_kvsdir_t **dir);
 int flux_kvs_lookup_get_symlink (flux_future_t *f,
diff --git a/src/common/libkvs/kvs_txn.c b/src/common/libkvs/kvs_txn.c
index f362588709f5..ca4e08dfced3 100644
--- a/src/common/libkvs/kvs_txn.c
+++ b/src/common/libkvs/kvs_txn.c
@@ -101,7 +101,7 @@ int flux_kvs_txn_put_raw (flux_kvs_txn_t *txn,
                           int flags,
                           const char *key,
                           const void *data,
-                          int len)
+                          size_t len)
 {
     json_t *dirent = NULL;
     int saved_errno;
diff --git a/src/common/libkvs/kvs_txn.h b/src/common/libkvs/kvs_txn.h
index 4ebd89b052b4..d884afb16754 100644
--- a/src/common/libkvs/kvs_txn.h
+++ b/src/common/libkvs/kvs_txn.h
@@ -43,7 +43,7 @@ int flux_kvs_txn_put_raw (flux_kvs_txn_t *txn,
                           int flags,
                           const char *key,
                           const void *data,
-                          int len);
+                          size_t len);
 
 int flux_kvs_txn_put_treeobj (flux_kvs_txn_t *txn,
                               int flags,
diff --git a/src/common/libkvs/kvs_txn_compact.c b/src/common/libkvs/kvs_txn_compact.c
index 751935558469..827e67a88bf4 100644
--- a/src/common/libkvs/kvs_txn_compact.c
+++ b/src/common/libkvs/kvs_txn_compact.c
@@ -51,7 +51,7 @@
 
 struct append_data {
     void *data;
-    int len;
+    size_t len;
 };
 
 struct compact_key {
diff --git a/src/common/libkvs/test/kvs_txn.c b/src/common/libkvs/test/kvs_txn.c
index 175b5b23aec1..d582ce1f0335 100644
--- a/src/common/libkvs/test/kvs_txn.c
+++ b/src/common/libkvs/test/kvs_txn.c
@@ -37,7 +37,7 @@ void jdiag (json_t *o)
 int check_null_value (json_t *dirent)
 {
     char *data = "";
-    int len = -1;
+    size_t len = 42;
 
     if (treeobj_decode_val (dirent, (void **)&data, &len) < 0) {
         diag ("%s: initial base64 decode failed", __FUNCTION__);
@@ -56,7 +56,8 @@ int check_null_value (json_t *dirent)
 int check_int_value (json_t *dirent, int expected)
 {
     char *data;
-    int rc, len, i;
+    int rc, i;
+    size_t len;
     json_t *val;
 
     if (treeobj_decode_val (dirent, (void **)&data, &len) < 0) {
@@ -89,7 +90,8 @@ int check_int_value (json_t *dirent, int expected)
 int check_string_value (json_t *dirent, const char *expected)
 {
     char *data;
-    int rc, len;
+    int rc;
+    size_t len;
     const char *s;
     json_t *val;
 
@@ -121,7 +123,7 @@ int check_string_value (json_t *dirent, const char *expected)
 int check_raw_value (json_t *dirent, const char *expected, int expected_len)
 {
     char *data;
-    int len;
+    size_t len;
 
     if (treeobj_decode_val (dirent, (void **)&data, &len) < 0) {
         diag ("%s: initial base64 decode failed", __FUNCTION__);
@@ -304,7 +306,8 @@ void test_raw_values (void)
     char buf[13], *nbuf;
     json_t *entry, *dirent;
     const char *key;
-    int flags, nlen;
+    int flags;
+    size_t nlen;
 
     memset (buf, 'c', sizeof (buf));
 
diff --git a/src/common/libkvs/test/kvs_txn_compact.c b/src/common/libkvs/test/kvs_txn_compact.c
index b61bfebe49eb..377bcd3e1aee 100644
--- a/src/common/libkvs/test/kvs_txn_compact.c
+++ b/src/common/libkvs/test/kvs_txn_compact.c
@@ -29,7 +29,7 @@
 int check_null_value (json_t *dirent)
 {
     char *data = "";
-    int len = -1;
+    size_t len = 42;
 
     if (treeobj_decode_val (dirent, (void **)&data, &len) < 0) {
         diag ("%s: initial base64 decode failed", __FUNCTION__);
@@ -45,7 +45,7 @@ int check_null_value (json_t *dirent)
 int check_raw_value (json_t *dirent, const char *expected, int expected_len)
 {
     char *data = NULL;
-    int len;
+    size_t len;
     int rc = -1;
 
     if (treeobj_decode_val (dirent, (void **)&data, &len) < 0) {
diff --git a/src/common/libkvs/test/treeobj.c b/src/common/libkvs/test/treeobj.c
index d94a45aad55c..8413c6a6ad42 100644
--- a/src/common/libkvs/test/treeobj.c
+++ b/src/common/libkvs/test/treeobj.c
@@ -191,7 +191,7 @@ void test_val (void)
     json_t *val, *val2;
     char buf[32];
     char *outbuf;
-    int outlen;
+    size_t outlen;
 
     memset (buf, 'x', sizeof (buf));
 
@@ -720,7 +720,7 @@ void test_corner_cases (void)
     json_t *val, *valref, *dir, *symlink;
     json_t *array, *object;
     char *outbuf;
-    int outlen;
+    size_t outlen;
 
     val = treeobj_create_val ("a", 1);
     if (!val)
diff --git a/src/common/libkvs/treeobj.c b/src/common/libkvs/treeobj.c
index e9e167b70979..e45efd453782 100644
--- a/src/common/libkvs/treeobj.c
+++ b/src/common/libkvs/treeobj.c
@@ -218,7 +218,7 @@ int treeobj_get_symlink (const json_t *obj,
     return 0;
 }
 
-int treeobj_decode_val (const json_t *obj, void **dp, int *lp)
+int treeobj_decode_val (const json_t *obj, void **dp, size_t *lp)
 {
     const char *type, *xdatastr;
     const json_t *xdata;
@@ -517,9 +517,9 @@ json_t *treeobj_create_symlink (const char *ns, const char *target)
     return obj;
 }
 
-json_t *treeobj_create_val (const void *data, int len)
+json_t *treeobj_create_val (const void *data, size_t len)
 {
-    int xlen;
+    ssize_t xlen;
     char *xdata;
     json_t *obj = NULL;
 
diff --git a/src/common/libkvs/treeobj.h b/src/common/libkvs/treeobj.h
index 867aaf00302b..f0ec1c01ee0a 100644
--- a/src/common/libkvs/treeobj.h
+++ b/src/common/libkvs/treeobj.h
@@ -24,7 +24,7 @@
  * Return JSON object on success, NULL on failure with errno set.
  */
 json_t *treeobj_create_symlink (const char *ns, const char *target);
-json_t *treeobj_create_val (const void *data, int len);
+json_t *treeobj_create_val (const void *data, size_t len);
 json_t *treeobj_create_valref (const char *blobref);
 json_t *treeobj_create_dir (void);
 json_t *treeobj_create_dirref (const char *blobref);
@@ -67,7 +67,7 @@ int treeobj_get_symlink (const json_t *obj,
  * If len > 0, data will be followed by an extra NULL byte in memory.
  * Caller must free returned data.
  */
-int treeobj_decode_val (const json_t *obj, void **data, int *len);
+int treeobj_decode_val (const json_t *obj, void **data, size_t *len);
 
 /* get type-specific count.
  * For dirref/valref, this is the number of blobrefs.
diff --git a/src/common/librouter/test/sendfd.c b/src/common/librouter/test/sendfd.c
index d74e53822781..4d0d3f67139d 100644
--- a/src/common/librouter/test/sendfd.c
+++ b/src/common/librouter/test/sendfd.c
@@ -68,7 +68,7 @@ void test_large (void)
     char buf[8192];
     const char *topic;
     const void *buf2;
-    int buf2len;
+    size_t buf2len;
 #if defined(F_GETPIPE_SZ)
     int min_size = 16384;
     int size;
@@ -280,7 +280,7 @@ void test_nonblock (int size, int count)
     while ((msg = zlist_pop (ior->queue))) {
         const char *topic;
         const void *buf2;
-        int buf2len;
+        size_t buf2len;
 
         if (flux_request_decode_raw (msg, &topic, &buf2, &buf2len) < 0) {
             diag ("flux_request_decode_raw: %s", flux_strerror (errno));
diff --git a/src/common/librouter/test/usock_echo.c b/src/common/librouter/test/usock_echo.c
index 08ebffcf92bb..f36252b400f2 100644
--- a/src/common/librouter/test/usock_echo.c
+++ b/src/common/librouter/test/usock_echo.c
@@ -139,7 +139,7 @@ static bool equal_message (const flux_msg_t *m1, const flux_msg_t *m2)
     int type1, type2;
     const char *topic1, *topic2;
     const void *buf1, *buf2;
-    int len1, len2;
+    size_t len1, len2;
 
     if (flux_msg_get_type (m1, &type1) < 0)
         return false;
diff --git a/src/modules/content-files/content-files.c b/src/modules/content-files/content-files.c
index 2b10b6fce833..b5c3fad8db6e 100644
--- a/src/modules/content-files/content-files.c
+++ b/src/modules/content-files/content-files.c
@@ -122,7 +122,7 @@ static void load_cb (flux_t *h,
 {
     struct content_files *ctx = arg;
     const void *hash;
-    int hash_size;
+    size_t hash_size;
     char blobref[BLOBREF_MAX_STRING_SIZE];
     void *data = NULL;
     size_t size;
@@ -164,7 +164,7 @@ void store_cb (flux_t *h,
 {
     struct content_files *ctx = arg;
     const void *data;
-    int size;
+    size_t size;
     char blobref[BLOBREF_MAX_STRING_SIZE];
     char hash[BLOBREF_MAX_DIGEST_SIZE];
     int hash_size;
diff --git a/src/modules/content-s3/content-s3.c b/src/modules/content-s3/content-s3.c
index c5e84c0b3162..4f39e140851f 100644
--- a/src/modules/content-s3/content-s3.c
+++ b/src/modules/content-s3/content-s3.c
@@ -256,7 +256,7 @@ static void load_cb (flux_t *h, flux_msg_handler_t *mh, const flux_msg_t *msg, v
 {
     struct content_s3 *ctx = arg;
     const void *hash;
-    int hash_size;
+    size_t hash_size;
     char blobref[BLOBREF_MAX_STRING_SIZE];
     void *data = NULL;
     size_t size;
@@ -300,7 +300,7 @@ void store_cb (flux_t *h,
 {
     struct content_s3 *ctx = arg;
     const void *data;
-    int size;
+    size_t size;
     char blobref[BLOBREF_MAX_STRING_SIZE];
     uint8_t hash[BLOBREF_MAX_DIGEST_SIZE];
     int hash_size;
diff --git a/src/modules/content-sqlite/content-sqlite.c b/src/modules/content-sqlite/content-sqlite.c
index 5778333c86db..312d8060e1dc 100644
--- a/src/modules/content-sqlite/content-sqlite.c
+++ b/src/modules/content-sqlite/content-sqlite.c
@@ -305,7 +305,7 @@ static void load_cb (flux_t *h,
 {
     struct content_sqlite *ctx = arg;
     const void *hash;
-    int hash_size;
+    size_t hash_size;
     const void *data;
     int size;
     struct timespec t0;
@@ -339,7 +339,7 @@ void store_cb (flux_t *h,
 {
     struct content_sqlite *ctx = arg;
     const void *data;
-    int size;
+    size_t size;
     uint8_t hash[BLOBREF_MAX_DIGEST_SIZE];
     int hash_size;
     struct timespec t0;
diff --git a/src/modules/content/cache.c b/src/modules/content/cache.c
index 6d4da698e9ce..b543f397fa7a 100644
--- a/src/modules/content/cache.c
+++ b/src/modules/content/cache.c
@@ -62,7 +62,7 @@ struct msgstack {
 
 struct cache_entry {
     const void *data;
-    int len;
+    size_t len;
     void *data_container;
     void *hash;                     // key storage is contiguous with struct
     uint8_t valid:1;                // entry contains valid data
@@ -417,7 +417,7 @@ static void content_load_request (flux_t *h,
 {
     struct content_cache *cache = arg;
     const void *hash;
-    int hash_size;
+    size_t hash_size;
     struct cache_entry *e;
     const char *errmsg = NULL;
 
@@ -535,7 +535,7 @@ static void cache_store_continuation (flux_future_t *f, void *arg)
     struct content_cache *cache = arg;
     struct cache_entry *e = flux_future_aux_get (f, "entry");
     const void *hash;
-    int hash_size;
+    size_t hash_size;
 
     e->store_pending = 0;
     assert (cache->flush_batch_count > 0);
@@ -630,7 +630,7 @@ static void content_store_request (flux_t *h,
 {
     struct content_cache *cache = arg;
     const void *data;
-    int len;
+    size_t len;
     struct cache_entry *e = NULL;
     uint8_t hash[BLOBREF_MAX_DIGEST_SIZE];
     int hash_size;
diff --git a/src/modules/kvs-watch/kvs-watch.c b/src/modules/kvs-watch/kvs-watch.c
index 9de18ccacde2..5f3e0609d576 100644
--- a/src/modules/kvs-watch/kvs-watch.c
+++ b/src/modules/kvs-watch/kvs-watch.c
@@ -255,7 +255,7 @@ static void handle_load_response (flux_future_t *f, struct watcher *w)
 {
     flux_t *h = flux_future_get_flux (f);
     const void *data;
-    int size;
+    size_t size;
     flux_error_t err;
 
     if (content_load_get (f, &data, &size) < 0) {
diff --git a/src/modules/kvs/kvs.c b/src/modules/kvs/kvs.c
index 9259c56d1274..d36229b24fe2 100644
--- a/src/modules/kvs/kvs.c
+++ b/src/modules/kvs/kvs.c
@@ -501,7 +501,7 @@ static void content_load_completion (flux_future_t *f, void *arg)
 {
     struct kvs_ctx *ctx = arg;
     const void *data;
-    int size;
+    size_t size;
     const char *blobref;
     struct cache_entry *entry;
 
diff --git a/t/request/req.c b/t/request/req.c
index c384b9723433..ec86c342f019 100644
--- a/t/request/req.c
+++ b/t/request/req.c
@@ -305,7 +305,8 @@ void null_request_cb (flux_t *h,
 {
     t_req_ctx_t *ctx = arg;
     const char *topic;
-    int type, size;
+    int type;
+    size_t size;
     const void *buf;
     uint32_t nodeid;
 
@@ -349,7 +350,7 @@ void null_request_cb (flux_t *h,
     if (flux_msg_get_payload (msg, &buf, &size) == 0) {
         flux_log (h,
                   LOG_ERR,
-                  "%s: unexpected payload size %d",
+                  "%s: unexpected payload size %zu",
                   __FUNCTION__,
                   size);
         goto error;
diff --git a/t/request/rpc.c b/t/request/rpc.c
index fd0e262865ff..c834e6da385b 100644
--- a/t/request/rpc.c
+++ b/t/request/rpc.c
@@ -41,7 +41,7 @@ int main (int argc, char *argv[])
     ssize_t inlen;
     void *inbuf;
     const char *outbuf;
-    int outlen;
+    size_t outlen;
     int expected_errno = -1;
     int ch;
     bool raw_request = false;