What does "loose coupling" mean between services?

Loose coupling is a principle in which microservices depend on each other as little as possible. Each service can be changed, restarted, or replaced without affecting the others.

#The essence

The connection between services is built through clear interfaces (APIs), not through shared code or a database. One service only knows what the other does, not how it is built.

Example: The orders service calls the payments API POST /payments, but it does not care what the payments service is written in or how it stores data.

#Why this matters

• Lets you develop and update services independently.
• Increases resilience: a failure in one service does not break the others.
• Simplifies scaling and swapping technologies.

#How it is achieved

• Communication only through APIs or message queues.
• Isolated databases.
• API contracts and versions so that changes do not break other services.
• Using asynchronous events instead of direct calls where possible.

Summary:

Loose coupling means services talk to each other but do not depend on each other. They are connected logically but isolated technically, like independent participants in one ecosystem.