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Bug: Kafka consumer fails esbuild bundling unless unused Avro and Protobuf dependencies are installed #5557
Description
Expected Behavior
A primitive-only consumer should bundle with only @aws-lambda-powertools/kafka installed. Format-specific dependencies and implementation code should only be required when Avro or Protobuf is configured.
Current Behavior
Using @aws-lambda-powertools/kafka@2.34.0 with primitive deserialization fails during esbuild bundling when avro-js and protobufjs are not installed.
The consumer dynamically imports all supported deserializers using literal paths. Esbuild resolves these modules during bundling, even though the handler does not configure Avro or Protobuf:
Could not resolve "protobufjs"
@aws-lambda-powertools/kafka/lib/esm/deserializer/protobuf.js:
import { BufferReader } from 'protobufjs';
Could not resolve "avro-js"
@aws-lambda-powertools/kafka/lib/esm/deserializer/avro.js:
import avro from 'avro-js';
The documentation indicates that these libraries are required only when their respective formats are used. They are also absent from the Kafka package’s dependencies and optional peer dependencies.
Installing both packages allows bundling, but esbuild includes both unused codec implementations in the single-file Lambda bundle because they remain runtime-selectable.
Occurs in invoking esbuild directly (see below) and CDK NodeJsFunctio bundling.
Code snippet
import { kafkaConsumer } from '@aws-lambda-powertools/kafka';
export const handler = kafkaConsumer(async (event) => {
for (const record of event.records) {
console.log(record.value);
}
});Steps to Reproduce
mkdir powertools-kafka-repro
cd powertools-kafka-repro
npm init -y
npm install @aws-lambda-powertools/kafka@2.34.0
npm install --save-dev esbuildCreate index.ts:
import { kafkaConsumer } from '@aws-lambda-powertools/kafka';
export const handler = kafkaConsumer(async (event) => {
for (const record of event.records) {
console.log(record.value);
}
});Bundle it:
npx esbuild index.ts \
--bundle \
--platform=node \
--target=node24 \
--format=esm \
--outfile=dist/index.mjsPossible Solution
No response
Powertools for AWS Lambda (TypeScript) version
latest
AWS Lambda function runtime
24.x
Packaging format used
npm
Activity
powertools-for-aws-oss-automation commentedon Aug 14, 2026
Thanks for opening your first issue here! We'll come back to you as soon as we can.
In the meantime, check out our GitHub Discussions: Join the conversation
fix(kafka): lazily import Avro and Protobuf codecs so JSON-only consu…
fix(kafka): lazily import Avro and Protobuf codecs so JSON-only consu…
fix(kafka): lazily import Avro and Protobuf codecs so JSON-only consu…
powertools-for-aws-oss-automation commentedon Aug 25, 2026
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svozza commentedon Aug 25, 2026
This has been fixed in #5578.