The HTTP/2 Multiplexing Advantage

gRPC leverages HTTP/2's multiplexing capabilities to transmit multiple streams over a single persistent connection, eliminating the connection overhead that plagues REST APIs. Each gRPC call becomes a lightweight stream rather than a full HTTP request cycle, resulting in significantly lower latency for request-heavy workloads. This is particularly valuable in microservices architectures where services exchange dozens of calls per second. REST, bound to HTTP/1.1 (or HTTP/1.1-style semantics in HTTP/2), requires new connections or connection pooling, making it less efficient for high-frequency inter-service communication.

The performance gain becomes measurable when you're handling hundreds of concurrent operations. With gRPC, you can push multiple requests through a single connection without head-of-line blocking, while REST implementations need careful tuning of connection pools and timeouts to achieve similar throughput.

Schema-Driven Development vs Flexibility

Protocol Buffers enforce strong typing and client generation, eliminating boilerplate but creating a hard dependency on the protobuf toolchain. This works well in closed environments where all services are under your control. REST's JSON payloads sacrifice efficiency for human readability and tooling ubiquity, making debugging trivial with curl or browser developer tools.

Bidirectional Streaming and Real-Time Patterns

gRPC's native bidirectional streaming support enables communication patterns impossible with REST. Server-initiated pushes, event streams, and long-lived connections are first-class citizens in gRPC, not afterthoughts requiring WebSockets or polling workarounds. This means lower latency for real-time features like live notifications, collaborative editing, or metric streaming in monitoring systems.

REST implementations must resort to workarounds: chunked responses for server pushes, polling for bidirectional patterns, or WebSocket bridges that add complexity and operational overhead. For services that need true asynchronous, event-driven communication, gRPC's streaming model eliminates an entire class of architectural decisions.

Applied Insight: When to Choose Which

Use gRPC for internal service-to-service communication in microservices architectures, especially when you need bidirectional streaming, low latency at scale, or high-frequency API calls. The schema-first approach and code generation reduce operational friction when services are tightly coordinated. Use REST for public APIs, third-party integrations, and scenarios where tooling ubiquity and human readability matter more than raw throughput. REST's widespread browser support and ecosystem of debugging tools make it the default choice when interfacing with external consumers who may not want to integrate Protocol Buffers or gRPC clients.

The hybrid approach works best: expose internal services via gRPC while maintaining a REST API layer for public consumption, accepting the translation cost for better developer experience and ecosystem compatibility.