gRPC vs REST Performance Comparison

gRPC is faster than REST for internal service calls for two compounding reasons: smaller payloads from Protocol Buffers and connection efficiency from HTTP/2. At scale, these savings compound in ways that REST's simplicity cannot offset.

Protocol Buffers — the payload advantage:

• Binary encoding with field numbers instead of repeated key names produces payloads 3–10× smaller than JSON; a list of 1,000 objects avoids repeating field names like "orderId", "customerId", "amount" for every element
• The compiled schema means deserialization is a direct memory copy instead of runtime character scanning, string escaping, and type inference; at 10K messages per second, the CPU savings alone are measurable — roughly 20–30% of a CPU core

HTTP/2 multiplexing — the connection advantage:

• All RPCs share one persistent TCP connection with full multiplexing — multiple in-flight requests without head-of-line blocking
• REST over HTTP/1.1 needs a new connection per request or connection pooling to approach similar efficiency; every new connection repeats the TCP and TLS handshake cost

Where the advantages compound:

• In service mesh scenarios with multiple hops, saving 5ms per hop across five services produces 25ms aggregate improvement on a single user request — the deeper the call chain, the larger the total payoff
• Teams have reported cutting internal latency by 60–70% switching high-frequency REST calls to gRPC on measured hot paths

When gRPC's advantages don't matter:

• Below roughly 1,000 requests per second, the performance difference is unmeasurable; REST's debuggability with curl, Postman, and browser tooling is a real advantage that gRPC cannot match

I recommend gRPC for east-west traffic on high-RPS internal paths where the performance savings are measurable, and REST at the edge and for low-traffic internal endpoints where debuggability matters more than microseconds.