Appwrite combines Auth, TablesDB, Storage, Functions, Realtime, and Messaging behind consistent APIs; Cloud and self-hosted products resemble each other but have different operational ownership.
Convex combines typed backend functions, a transactional document database, and reactive query subscriptions; correctness depends on separating deterministic mutations from side-effecting actions.
Firebase moves quickly because client SDKs directly access managed Auth, Firestore, and Storage; the real backend contract lives in data models, Security Rules, Functions, and cost limits.
Nhost uses PostgreSQL as the source of truth, Hasura to generate GraphQL, and connects Auth claims, role permissions, Storage, and Functions into one platform.
PocketBase packages SQLite, collections, Auth, file storage, SSE realtime, and an admin UI into a small executable; deployment is easy, but single-host and pre-v1 compatibility limits matter.
Supabase isn't just an open-source Firebase alternative — its core design builds Auth, Storage, and Realtime entirely on PostgreSQL schemas and WAL. The result: everything is queryable with SQL, pgvector works out of the box, and AI agents can operate the entire platform by writing SQL. 108k GitHub stars, Apache 2.0, free tier with 500 MB database.