Strata Sync vs Convex

Both are worth using. They disagree about one thing, and almost everything else follows from it: who owns the database.

Who owns the data

Convex brings its own managed database. Your data lives inside it, and one product holds the data, runs the functions and pushes updates. Strata Sync owns nothing. @stratasync/server adds routes to the Fastify app you already deploy and writes its log into the Postgres you already run. Anything else reading that database keeps working.

If you are starting fresh and want one product to own the backend, that is a real advantage and Convex is good at it. If the database already exists and has to stay yours, no feature list changes the answer.

How writes work

In Convex, writes are server functions: transactional, called from the client, with a natural home for validation. In Strata Sync the client has a durable outbox. A change applies at once and queues until the server confirms it through /sync/mutate, with idempotency keys so a retry never applies twice.

Where they agree

More than the framing suggests. Convex uses optimistic concurrency control with a strictly increasing sequence id. Strata Sync gives every change a monotonic syncId and has clients replay that order. Both are server-authoritative, and both let a client catch up by asking for everything after a number. Strata Sync also resolves conflicts per field, so two people editing different fields of one row never collide.

Collaborative text

Neither ships it in the core model, for the same reason: server ordering handles two people typing in one paragraph badly. Strata Sync includes Yjs documents and presence in @stratasync/y-doc. With Convex you bring your own CRDT.

Choosing

• Convex when you want one product to own the backend, you have no existing Postgres, and you want a company behind it.
• Strata Sync when the database must stay yours, you want Linear’s architecture, or you need undo and collaborative text without assembling them.

Convex is a funded product with a team. Strata Sync is one author plus contributors, in production on one product, MIT licensed. That is a real argument for Convex if support matters more than owning the stack. For the wider field, see the sync engine comparison.