Conclusion

This chapter covered one rule with large consequences. Each microservice owns one private data store. Every other service reaches that data only through its API. This lesson recaps what the rule gives you, what it costs, and where the course goes next.

What the Pattern Gives You

The gains all come from one source: each service is the only writer and the only reader of its own tables. Nothing outside the service can depend on its schema.

That single fact produces four practical gains:

• Independent schema changes. A team can rename a column without breaking anyone.