Every service you add buys you one thing and costs you several. Here is how to tell when the trade is worth it, using what Amazon, Uber, Shopify, Segment and others have said in public.

A function call inside one process is cheap and almost never fails. A call to another service crosses a network. It can be slow, drop, time out, or arrive twice.

Microservices turn many function calls into network calls. That is the whole trade. You get independent deploys and independent scaling. You pay with latency, new failure modes, and a lot more to operate.

My view is simple: pay that price only when you have a problem that services actually solve. Below are the costs, what well-known companies did, when services are the right call, and a middle path you can start on Monday. Every claim links to its source right where it appears.

The cost nobody puts on the slide

First, a plain definition. A microservice is a small application that runs on its own and is called over the network.…