diff --git a/headerforwarder/forwarder.go b/headerforwarder/forwarder.go
index 75b7ae50..13576564 100644
--- a/headerforwarder/forwarder.go
+++ b/headerforwarder/forwarder.go
@@ -19,6 +19,7 @@ import (
 	"fmt"
 	"net/http"
 	"strings"
+	"sync"
 
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/metadata"
@@ -36,7 +37,9 @@ import (
 // TODO: this should expire entries after a certain amount of time
 type HeaderForwarder struct {
 	incomingHeaders    map[string]http.Header
+	incomingHeaderLock sync.RWMutex
 	outgoingHeaders    map[string]http.Header
+	outgoingHeaderLock sync.RWMutex
 	interestingHeaders []string
 	actualTransport    http.RoundTripper
 }
@@ -66,14 +69,20 @@ func (hf *HeaderForwarder) captureOutgoingHeaders(req *http.Request) {
 	ctx := req.Context()
 	rosettaRequestID := RosettaIDFromContext(ctx)
 
-	hf.outgoingHeaders[rosettaRequestID] = make(http.Header)
+	// We don't worry about overwriting headers here because we only handle "outgoing" headers
+	// once: when the rosetta request is made
+	outgoingRequestHeaders := make(http.Header)
 
 	// Only capture interesting headers
 	for _, interestingHeader := range hf.interestingHeaders {
 		if _, requestHasHeader := req.Header[http.CanonicalHeaderKey(interestingHeader)]; requestHasHeader {
-			hf.outgoingHeaders[rosettaRequestID].Set(interestingHeader, req.Header.Get(interestingHeader))
+			outgoingRequestHeaders.Set(interestingHeader, req.Header.Get(interestingHeader))
 		}
 	}
+
+	hf.outgoingHeaderLock.Lock()
+	hf.outgoingHeaders[rosettaRequestID] = outgoingRequestHeaders
+	hf.outgoingHeaderLock.Unlock()
 }
 
 // shouldRememberHeaders reports whether response headers should be remembered for a
@@ -113,7 +122,10 @@ func (hf *HeaderForwarder) rememberHeaders(req *http.Request, resp *http.Respons
 
 	// For multiple requests with the same rosetta ID, we want to remember all of the headers
 	// For repeated response headers, later values will overwrite earlier ones
+	hf.incomingHeaderLock.RLock()
 	headersToRemember, exists := hf.incomingHeaders[rosettaRequestID]
+	hf.incomingHeaderLock.RUnlock()
+
 	if !exists {
 		headersToRemember = make(http.Header)
 	}
@@ -123,7 +135,9 @@ func (hf *HeaderForwarder) rememberHeaders(req *http.Request, resp *http.Respons
 		headersToRemember.Set(interestingHeader, resp.Header.Get(interestingHeader))
 	}
 
+	hf.incomingHeaderLock.Lock()
 	hf.incomingHeaders[rosettaRequestID] = headersToRemember
+	hf.incomingHeaderLock.Unlock()
 }
 
 // shouldRememberMetadata reports whether response metadata should be remembered for a grpc unary
@@ -152,7 +166,10 @@ func (hf *HeaderForwarder) rememberMetadata(ctx context.Context, resp metadata.M
 
 	// For multiple requests with the same rosetta ID, we want to remember all of the headers
 	// For repeated response headers, later values will overwrite earlier ones
+	hf.incomingHeaderLock.RLock()
 	headersToRemember, exists := hf.incomingHeaders[rosettaID]
+	hf.incomingHeaderLock.RUnlock()
+
 	if !exists {
 		headersToRemember = make(http.Header)
 	}
@@ -163,20 +180,28 @@ func (hf *HeaderForwarder) rememberMetadata(ctx context.Context, resp metadata.M
 		}
 	}
 
+	hf.incomingHeaderLock.Lock()
 	hf.incomingHeaders[rosettaID] = headersToRemember
+	hf.incomingHeaderLock.Unlock()
 }
 
 // GetResponseHeaders returns any headers that should be returned to a rosetta response. These
 // consist of native node response headers/metadata that were remembered for a request ID.
 func (hf *HeaderForwarder) getResponseHeaders(rosettaRequestID string) (http.Header, bool) {
+	hf.incomingHeaderLock.RLock()
 	headers, ok := hf.incomingHeaders[rosettaRequestID]
+	hf.incomingHeaderLock.RUnlock()
 
 	// Delete the headers from the map after they are retrieved
 	// This is safe to call even if the key doesn't exist
+	hf.incomingHeaderLock.Lock()
 	delete(hf.incomingHeaders, rosettaRequestID)
+	hf.incomingHeaderLock.Unlock()
 
 	// Also delete the outgoing headers from the map since we are done with them
+	hf.outgoingHeaderLock.Lock()
 	delete(hf.outgoingHeaders, rosettaRequestID)
+	hf.outgoingHeaderLock.Unlock()
 
 	return headers, ok
 }
@@ -209,8 +234,12 @@ func (hf *HeaderForwarder) HeaderForwarderHandler(next http.Handler) http.Handle
 // RoundTrip implements http.RoundTripper and will be used to construct an http Client which
 // saves the native node response headers if necessary.
 func (hf *HeaderForwarder) RoundTrip(req *http.Request) (*http.Response, error) {
+	hf.outgoingHeaderLock.RLock()
+	outgoingHeaders, hasOutgoingHeaders := hf.outgoingHeaders[RosettaIDFromRequest(req)]
+	hf.outgoingHeaderLock.RUnlock()
+
 	// add outgoing headers to the request
-	if outgoingHeaders, ok := hf.outgoingHeaders[RosettaIDFromRequest(req)]; ok {
+	if hasOutgoingHeaders {
 		for header, values := range outgoingHeaders {
 			for _, value := range values {
 				req.Header.Add(header, value)
@@ -227,13 +256,18 @@ func (hf *HeaderForwarder) RoundTrip(req *http.Request) (*http.Response, error)
 	return resp, err
 }
 
-func (hf *HeaderForwarder) UnaryClientInterceptor(ctx context.Context, method string, req, reply any, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
+func (hf *HeaderForwarder) UnaryClientInterceptor(ctx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
 	// Capture incoming headers from the grpc call
 	var header metadata.MD
 	opts = append(opts, grpc.Header(&header))
 
+	// Get outgoing headers from the request ID in context
+	hf.outgoingHeaderLock.RLock()
+	outgoingHeaders, hasOutgoingHeaders := hf.outgoingHeaders[RosettaIDFromContext(ctx)]
+	hf.outgoingHeaderLock.RUnlock()
+
 	// Add outgoing headers to the context
-	if outgoingHeaders, ok := hf.outgoingHeaders[RosettaIDFromContext(ctx)]; ok {
+	if hasOutgoingHeaders {
 		for header, values := range outgoingHeaders {
 			for _, value := range values {
 				ctx = metadata.AppendToOutgoingContext(ctx, strings.ToLower(header), value)