gRPC

Backend · Advanced · 5 min read

What is it?

gRPC is a high-performance framework for calling functions on a remote service as if they were local, using compact binary messages.

Explain like I'm 5

gRPC is like a direct phone line between two programs where they agree on a strict script in advance, so calls are fast and there's no confusion about what to say.

Why was it created?

It was built for fast, strongly-typed communication between microservices, where text-based REST/JSON adds overhead and ambiguity.

Where is it used?

Internal microservice communication
Low-latency backend systems
Polyglot service environments
Streaming data between services

Why should developers care?

gRPC is common in performance-sensitive backend systems and service meshes. Backend and platform engineers run into it often.

How does it work?

You define services and messages in a .proto file. gRPC generates client and server code, then sends compact binary messages over HTTP/2, which also enables streaming.

Real-world example

An order service calls an inventory service's CheckStock method directly through generated client code, getting a typed response in milliseconds.

Common use cases

Service-to-service calls
Low-latency, high-throughput APIs
Bidirectional streaming
Cross-language backends

Advantages

Fast, compact binary protocol
Strongly typed contracts
Built-in streaming over HTTP/2
Auto-generated client/server code

Disadvantages

Not natively supported in browsers
Harder to debug than plain JSON
More setup than REST

When should you use it?

For internal, performance-critical communication between services.

When should you avoid it?

For public browser-facing APIs where REST or GraphQL are easier to consume.

Alternatives

REST GraphQLApache Thrift

Interview questions

Beginner

What is gRPC used for?
What is a .proto file?

Intermediate

Why does gRPC use HTTP/2?
What is Protocol Buffers?

Senior

When would you choose gRPC over REST for an internal API?
How do you handle versioning of proto contracts?

Common misconceptions

"gRPC works directly in browsers" — browsers need a proxy layer (gRPC-Web).
"gRPC is only for Google" — it's open-source and widely used across the industry.

Fun facts

It uses Protocol Buffers to serialize messages compactly.
The 'g' is often said to stand for different words in each release, as a running joke.

Timeline

2016 — Released as open-source by Google

Learning resources

Official documentation

Quick summary

gRPC is a fast, strongly-typed framework for service-to-service calls using binary messages over HTTP/2.

Cheat sheet

Remote procedure calls (RPC)
Binary messages via Protocol Buffers
Runs over HTTP/2 with streaming
Best for internal services

If you remember only one thing

gRPC makes calling another service feel like calling a local function — fast and strongly typed.