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June 6, 2026 ADR ADR Status: Accepted

ADR-002: gRPC for Internal Communication

Architecture ADR gRPC

Context

In a microservices architecture, services make frequent RPC calls to fetch lookup values, verify auth states, and trigger downstream processes. Using standard REST/JSON creates performance bottlenecks due to string serialization, lacks strict typing interfaces, and does not support streaming naturally.

Decision

We will use gRPC with Protocol Buffers for all synchronous, internal service-to-service communication. External traffic from users will still enter through HTTP/JSON or GraphQL via our API Gateway, which will translate incoming payloads to internal gRPC requests.

Consequences

  • Pros:
    • Highly optimized serialization and deserialization speeds.
    • Multi-language support with automatic code generation from .proto definition files.
    • Strongly typed communication contracts checked at compile-time.
    • Out-of-the-box support for client, server, and bidirectional streaming.
  • Cons:
    • Human readability is reduced compared to JSON (requires tools like grpcurl or UI debuggers like Postman/BloomRPC).
    • Requires maintaining a schema definition workflow (e.g. shared repo or registry) to prevent breaking API contracts.