Microservice Architecture

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Pattern: API Composition

pattern   service collaboration   implementing queries  

Want to learn more about this pattern?

Take a look at my self-paced, online bootcamp that teaches you how to use the Saga, API Composition, and CQRS patterns to design operations that span multiple services.

The regular price is $395/person but use coupon OFFEFKCW to sign up for $95 (valid until Sept 30th, 2025)

Context

You have applied the Microservices architecture pattern and the Database per service pattern. As a result, it is no longer straightforward to implement queries that join data from multiple services.

Problem

How to implement queries in a microservice architecture?

Solution

Implement a query by defining an API Composer, which invoking the services that own the data and performs an in-memory join of the results.

Example

An API Gateway often does API composition.

Resulting context

This pattern has the following benefits:

  • It a simple way to query data in a microservice architecture

This pattern has the following drawbacks:

  • Some queries would result in inefficient, in-memory joins of large datasets.

See also

Learn more

  • My book Microservices patterns describes this pattern in a lot more detail
  • Take a look at my self-paced, online bootcamp that teaches you how to use the Saga, API Composition, and CQRS patterns to design operations that span multiple services.
pattern   service collaboration   implementing queries  
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