diff --git a/beavers/kafka.py b/beavers/kafka.py
index 4dc7f10..e967554 100644
--- a/beavers/kafka.py
+++ b/beavers/kafka.py
@@ -4,7 +4,7 @@
 import logging
 import time
 from enum import Enum
-from typing import Any, AnyStr, Generic, Optional, Protocol, TypeVar
+from typing import Any, AnyStr, Generic, Optional, Protocol, Sequence, TypeVar
 
 import confluent_kafka
 import confluent_kafka.admin
@@ -22,7 +22,7 @@
 class KafkaMessageDeserializer(Protocol[T]):
     """Interface for converting incoming kafka messages to custom data."""
 
-    def __call__(self, messages: list[confluent_kafka.Message]) -> T:
+    def __call__(self, messages: Sequence[confluent_kafka.Message]) -> T:
         """Convert batch of messages to data."""
 
 
@@ -38,7 +38,7 @@ class KafkaProducerMessage:
 class KafkaMessageSerializer(Protocol[T]):
     """Interface for converting custom data to outgoing kafka messages."""
 
-    def __call__(self, value: T) -> list[KafkaProducerMessage]:
+    def __call__(self, value: T) -> Sequence[KafkaProducerMessage]:
         """Convert batch of custom data to `KafkaProducerMessage`."""
 
 
@@ -384,29 +384,14 @@ def _update_partition_info(self, new_messages: list[confluent_kafka.Message]):
         )
 
 
-@dataclasses.dataclass(frozen=True)
-class _RuntimeSinkTopic:
-    nodes: list[Node]
-    serializer: KafkaMessageSerializer
-
-    def flush(self, cycle_id: int, producer_manger: _ProducerManager):
-        for node in self.nodes:
-            if node.get_cycle_id() == cycle_id:
-                node_value = node.get_sink_value()
-                # TODO: capture serialization time in metrics
-                messages = self.serializer(node_value)
-                for message in messages:
-                    producer_manger.produce_one(
-                        message.topic, message.key, message.value
-                    )
-
-
 @dataclasses.dataclass
 class ExecutionMetrics:
     """Metrics for the execution of a dag."""
 
     serialization_ns: int = 0
     serialization_count: int = 0
+    deserialization_ns: int = 0
+    deserialization_count: int = 0
     execution_ns: int = 0
     execution_count: int = 0
 
@@ -419,6 +404,15 @@ def measure_serialization_time(self):
             self.serialization_ns += time.time_ns() - before
             self.serialization_count += 1
 
+    @contextlib.contextmanager
+    def measure_deserialization_time(self):
+        before = time.time_ns()
+        try:
+            yield
+        finally:
+            self.deserialization_ns += time.time_ns() - before
+            self.deserialization_count += 1
+
     @contextlib.contextmanager
     def measure_execution_time(self):
         before = time.time_ns()
@@ -429,6 +423,20 @@ def measure_execution_time(self):
             self.execution_count += 1
 
 
+@dataclasses.dataclass(frozen=True)
+class _RuntimeSinkTopic:
+    nodes: list[Node]
+    serializer: KafkaMessageSerializer
+
+    def serialize(self, cycle_id: int) -> list[KafkaProducerMessage]:
+        messages = []
+        for node in self.nodes:
+            if node.get_cycle_id() == cycle_id:
+                node_value = node.get_sink_value()
+                messages.extend(self.serializer(node_value))
+        return messages
+
+
 class KafkaDriver:
     """Control the execution of a dag, using data from kafka."""
 
@@ -519,13 +527,19 @@ def _process_message(self, message: confluent_kafka.Message):
             self._source_topics[message.topic()].append(message)
 
     def _produce_records(self, cycle_id: int):
-        for sink_topic in self._sink_topics:
-            sink_topic.flush(cycle_id, self._producer_manager)
+        messages = []
+        with self._metrics.measure_serialization_time():
+            for sink_topic in self._sink_topics:
+                messages.extend(sink_topic.serialize(cycle_id))
+        for message in messages:
+            self._producer_manager.produce_one(
+                message.topic, message.key, message.value
+            )
 
     def _run_cycle(self, messages: list[confluent_kafka.Message]) -> bool:
         has_messages = False
-        with self._metrics.measure_serialization_time():
-            self._process_messages(messages)
+        self._process_messages(messages)
+        with self._metrics.measure_deserialization_time():
             for handler in self._source_topics.values():
                 has_messages = handler.flush() or has_messages
         cycle_time = (
@@ -652,7 +666,6 @@ def _get_previous_start_of_day(
     if (local_now - local_now.normalize()) > start_of_day_time:
         return (local_now.normalize() + start_of_day_time).tz_convert("UTC")
     else:
-        # TODO: consider adding calendar?
         return (
             local_now.normalize() - pd.to_timedelta("1d") + start_of_day_time
         ).tz_convert("UTC")
diff --git a/tests/test_kafka.py b/tests/test_kafka.py
index f0f6942..6ab0ad4 100644
--- a/tests/test_kafka.py
+++ b/tests/test_kafka.py
@@ -572,8 +572,10 @@ def test_kafka_driver_word_count(log_helper: LogHelper):
     assert len(log_helper.flush()) == 1
 
     metrics = kafka_driver.flush_metrics()
+    assert metrics.deserialization_ns > 0
+    assert metrics.deserialization_count == 6
     assert metrics.serialization_ns > 0
-    assert metrics.serialization_count == 6
+    assert metrics.serialization_count == 3
     assert metrics.execution_ns > 0
     assert metrics.execution_count == 3
 
@@ -1308,19 +1310,14 @@ def test_runtime_sink_topic():
     sink = dag.sink("sink", node)
     runtime_sink_topic = _RuntimeSinkTopic([sink], WorldCountSerializer("topic-1"))
 
-    producer_manager = MockProducerManager()
     dag.execute()
-    runtime_sink_topic.flush(dag.get_cycle_id(), producer_manager)
-    assert producer_manager.messages == []
+    assert runtime_sink_topic.serialize(dag.get_cycle_id()) == []
 
     node.set_stream({"foo": "bar"})
     dag.execute()
-    runtime_sink_topic.flush(dag.get_cycle_id(), producer_manager)
-    assert producer_manager.messages == [
+    assert runtime_sink_topic.serialize(dag.get_cycle_id()) == [
         KafkaProducerMessage(topic="topic-1", key=b"foo", value=b"bar")
     ]
-    producer_manager.messages.clear()
 
     dag.execute()
-    runtime_sink_topic.flush(dag.get_cycle_id(), producer_manager)
-    assert producer_manager.messages == []
+    assert runtime_sink_topic.serialize(dag.get_cycle_id()) == []