Communication Between Microservices: REST vs gRPC vs Events

Communication Between Microservices: REST vs gRPC vs Events

Microservices cannot share memory, so they talk over the network. The three common ways are REST, gRPC, and events.

REST (HTTP/JSON)

Use HTTP with JSON payloads. Pros: simple, universally supported, easy to debug with curl. Cons: verbose (JSON is text), no streaming of large payloads, higher latency than binary protocols.

gRPC (HTTP/2 with Protocol Buffers)

Use HTTP/2 with binary Protocol Buffers. Pros: fast, smaller payloads, supports streaming, generates client stubs. Cons: harder to debug (binary), needs protobuf schema, not browser-friendly without a gateway.

Events (Pub/Sub with Kafka, RabbitMQ, SQS)

Services publish and subscribe to events. Pros: decoupled, the producer does not need to know the consumers, handles bursts well, great for async work. Cons: eventual consistency, harder to debug, adds message broker setup.

When to Use Each

Use REST when:

• The consumer is external or a simple internal call.
• You need human-readable payloads.
• The service is not yet high-traffic.

Use gRPC when:

• Internal service-to-service calls with high traffic.
• You need streaming.
• You want typed schemas and fast serialization.

Use Events when:

• The action is async (e.g., user signed up, send a welcome email).
• Multiple consumers care about one event.
• You want to handle bursts without losing data.

Sync vs Async

REST and gRPC are sync (the caller waits for a response). Events are async (the publisher fires and moves on). Sync is simpler to reason about. Async scales better and decouples services.

The Takeaway

Use REST for simple or external calls, gRPC for high-traffic internal calls, and events for async or multi-consumer workflows. Sync is simpler; async decouples. Mix all three based on the need.