Misata vs Seedfast
These tools answer different questions. Seedfast asks what your schema permits and fills a Postgres database with data that fits it, which is a real job done well and the faster route if that is all you need. Misata asks what has to be true and generates data that satisfies it, then has an independent SQL engine confirm it did. The distinction matters the moment a number has to mean something: a quarterly total, an exact segment split, a parent aggregate that equals what its children sum to. Those facts live in your business logic, not in your schema, so no tool that reads only the schema can produce them. If you want an empty Postgres database filled quickly, Seedfast is the shorter path. If the data has to survive someone doing arithmetic on it, that is what Misata is for.
| Capability | Misata | Seedfast |
|---|---|---|
| Input it works from | A declaration, or an imported schema | Your live database schema |
| Databases supported | Postgres, MySQL, SQLite, plus CSV/JSON/SQL/Parquet | Postgres (MySQL, Oracle, SQLite in development) |
| Foreign keys, uniques, enums, checks | Yes | Yes, its core strength |
| Exact aggregates (a quarter that totals to target) | Yes, exact by construction | No |
| Cross-table reconciliation through a join path | Yes, verified | No |
| Reproducible output | Yes, identical bytes per seed | No, generates fresh each run |
| Independent verification of the result | Yes, a DuckDB check ships with the data | No |
| Runs without a database | Yes, generates to files | No, needs a live schema to read |
| Source available | MIT, open source | Closed source, account required |
| Entry price | Free and self-hosted, or credits in Studio | Free tier, then $16/mo |
| Reads schema changes automatically | Re-run the import | Yes, on every run |
A schema says what is allowed, not what is true
A CREATE TABLE statement is a precise document, and everything in it is about permission. A foreign key says a parent must exist, never that any value agrees with it. A CHECK constraint sees exactly one row of one table, which is why it can say a price is positive and cannot say that an order total equals the sum of its line items. That boundary is a property of SQL, not a gap in anyone's engineering, and it is the reason a tool whose only input is your schema cannot produce a reconciling total no matter how well it is built.
We measured the size of that gap
Misata's conformance suite is 126 SQL assertions over an 11-table schema. We took the same schema, stripped every declaration a CREATE TABLE could not carry, and ran the same engine at the same seed. Fifteen of the 126 assertions became unreachable: the multi-hop rollups, the payment sums bounded by their order, the declared missingness pattern, the late-arrival window, the exact duplicate count. Nothing about the generator changed. The information was simply no longer in the input. Those fifteen are a floor on what any schema-reading tool has to leave on the table, and the projection is in the repository so you can check the reduction yourself.
Where Seedfast is the better tool
If your requirement is an empty Postgres database that needs plausible rows this afternoon, Seedfast will get you there with less thinking. It reads the live schema on every run, so it never drifts out of sync with a migration, and that is genuinely nicer than re-running an import. Its planner keeps values coherent across a row, which is more than a Faker script gives you. Misata will ask you to say what the data has to prove, and if the honest answer is nothing in particular, that is overhead you do not need.
Reproducibility is the one to check before CI
Seedfast states that it generates fresh data on each run rather than deterministic output. For local development that is fine, and arguably preferable. For a test suite it is the difference between a failure you can investigate and one you cannot, because you cannot re-create the input that produced it. Misata is seeded end to end: the same schema and seed produce identical bytes, so a red build is reproducible on your machine.
Frequently asked
Is Misata a drop-in replacement for Seedfast?
Not exactly, because they start from different inputs. Seedfast points at a live Postgres schema; Misata can import a SQL, Prisma, or dbt schema and then seed a database, but it treats the schema as a starting point you add declarations to rather than the whole specification.
Does Misata respect check constraints and enums like Seedfast does?
Yes. Types, foreign keys, uniques, enums, and single-row constraints are all honoured. The difference is what sits on top: facts that span rows and tables, which a schema has no way to state.
Which is cheaper?
Misata's engine is MIT licensed and free to run yourself, with no account and no row cap. Studio, the hosted no-code surface, uses credits. Seedfast starts free and its paid plans begin at $16 a month. If cost is the deciding factor, running the open-source engine locally is the cheapest option available from either.
Can either tool anonymise my production data?
Neither. Seedfast says so directly on its own comparison pages, and Misata never sees your data by design. If masking a real database is the requirement, both of these are the wrong category of tool.
See Misata generate data for your domain