Hands-On Microservices with Kubernetes

Managing schema changes

One of the most challenging topics when working with relational databases is managing the SQL schema. When the schema changes, the change may be backward compatible (by adding a column) or non-backward compatible (by splitting a table into two separate tables). When the schema changes, we need to migrate our database, but also migrate the code that is affected by the schema change.

If you can afford a short downtime, then the process can be very simple, as follows:

1. Shut down all the impacted services and perform DB migration.
2. Deploy a new code that knows how to work with the new schema.
3. Everything just works.

However, if you need to keep the system running, you'll have to go through a more complicated process by ...