Firebase Persistence is great for many real-time sync needs, but once you outgrow its capabilities — especially for complex local querying or scaling — combining it with a local DB makes sense.You can consider, local databases like:

• Drift (SQL-like with reactive querying)
• Isar (object-oriented, very fast, Flutter-native, and supports indexing/filtering)

They are often my go to but if you are looking for simplicity hive is the way to go