Migrating an Existing App
Migrating an existing application to Citus sometimes requires adjusting the schema and queries for optimal performance. Citus extends PostgreSQL with distributed functionality, but Row-based sharding is not a drop-in replacement that scales out all workloads. A performant Citus cluster involves thinking about the data model, tooling, and choice of SQL features used.
There is another mode of operation in Citus called Schema-based sharding, and while Row-based sharding results in best performance and hardware efficiency, see schema based sharding if you are in a need for a more drop-in approach.
The first steps are to optimize the existing database schema so that it can work efficiently across multiple computers.
Next, update application code and queries to deal with the schema changes.
After testing the changes in a development environment, the last step is to migrate production data to a Citus cluster and switch over the production app. We have techniques to minimize downtime for this step.