gRPC, GraphQL, Protobuf, and API Contracts on AWS
Quick summary: Protobuf on the wire saves bytes; GraphQL saves round trips until resolvers N+1 your Aurora cluster. ALB gRPC, AppSync, and consumer-driven contracts with Pact.
Key Takeaways
- Protobuf on the wire saves bytes; GraphQL saves round trips until resolvers N+1 your Aurora cluster
- ALB (June 2026) supports gRPC over HTTP/2 to targets—health checks need gRPC-specific config
- AppSync hosts GraphQL with resolver mapping to Lambda/DynamoDB
- Idempotency keys HTTP header at API Gateway + DynamoDB store—required for payment mutations regardless of protocol
- What to do this week 1
Table of Contents
ALB (June 2026) supports gRPC over HTTP/2 to targets—health checks need gRPC-specific config. AppSync hosts GraphQL with resolver mapping to Lambda/DynamoDB.
Protocol choice
| Protocol | Wins | AWS surface |
|---|---|---|
| gRPC + protobuf | Streaming, typed contracts | ALB → ECS/EKS |
| GraphQL | Flexible reads | AppSync |
| REST + JSON | Ubiquitous | API Gateway HTTP API |
N+1 problem: GraphQL resolvers per field—batch with DataLoader pattern or AppSync pipeline resolvers.
Schema evolution
Protobuf: reserve fields, never reuse numbers. GraphQL: deprecate fields before removal. Pact consumer contracts in CI for internal microservices.
Idempotency keys
HTTP Idempotency-Key header at API Gateway + DynamoDB store—required for payment mutations regardless of protocol.
What to do this week
- Benchmark protobuf vs JSON on hottest endpoint—measure CPU not just bytes.
- Trace GraphQL resolver count per query in AppSync logs.
- Add breaking-change check in CI for
.protofiles.
What this guide doesn’t cover
OAuth—part 1 of API track.
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