Gmail: High-Level Design

Step 5: High-Level System Design

The last step defined the API. Now we lay out the services that sit behind it.

At a high level, this is a distributed system built from microservices. A microservice is a separate program with one job: sending mail, storing mail, searching, or filtering spam. Each one talks to the others over a defined API. Below are the major parts. After them, we walk through how one email moves through them.

API gateway and load balancers. This is the entry point for every client connection