API styles

REST, GraphQL, gRPC and webhooks: what each does, when to choose it, and the rules that avoid duplicates, broken clients and inconsistent lists.

The outline, topic by topic

Each topic is weighted the way the exam weighs it.

REST: what is it?
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An API style where resources identified by URLs are handled with HTTP methods.
Simple, widespread, and compatible with HTTP caching.
A mobile app must load profile, friends and notifications in one call, with only the displayed fields. Which style?
- GraphQL
- REST with three calls
- A webhook
- A message queue
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GraphQL
One query describes exactly what the screen needs.
GraphQL: what is it?
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A query language where the client asks for exactly the fields it wants, through a single endpoint.
The client avoids round trips and unneeded data.
What is a drawback of GraphQL?
- HTTP caching is harder and overly costly queries must be limited
- The client receives too much data
- One endpoint per resource is needed
- It only works internally
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HTTP caching is harder and overly costly queries must be limited
A client can write a huge query; safeguards are needed.