API Composition
A pattern where a composer service queries multiple microservices and joins the results in memory. The simplest way to implement cross-service queries.
What is API Composition?
A pattern where a composer service queries multiple microservices and joins the results in memory. The simplest way to implement cross-service queries.
API Composition is a intermediate-level concept that sits in the Microservices Architecture area of system design. Engineers reach for it whenever they need to reason about real-world trade-offs in that space — not just for textbook correctness, but because real production systems at companies like Netflix, Amazon, and Google make these decisions every day.
If you want to go deeper than this definition — with diagrams, code, and a quiz to lock it in — work through the "API Composition" lesson linked below. It walks through the why, the mechanism, the trade-offs, and how the giants actually use it in production.
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Full interactive lesson with diagrams, code examples, real-world references, and a quiz.
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See also
Related glossary terms you might want to look up next.
API Gateway
A single entry point for all client requests that routes them to the appropriate microservice. Handles auth, rate limiting, and request transformation.
Microservices
An architecture where an application is split into small, independent services that communicate over the network. Each service owns its own data and can be deployed separately.
CQRS
Command Query Responsibility Segregation: using different models for reading and writing data. Reads and writes have different performance needs, so separate them.