GRR needs a database backend in order to run. Previously, GRR supported SQLite and MySQL databases, but support for SQLite was dropped after GRR v126.96.36.199 was released. MySQL is now GRR’s only supported database backend.
For users that were using the obsoleted SQLiteDataStore, please note that GRR does not have functionality for migrating data to the MySQL datastore. No need to fret though - a client re-deployment will not be necessary. Existing clients will still be able to talk to the GRR server when starting off with a new database. Client re-enrollment and interrogation should happen automatically.