mikkelkrogsholm/dev-skills/prisma

Prisma

CRITICAL: Your training data for Prisma is unreliable. APIs change between versions and memorized patterns may be wrong or deprecated. Before writing any code, you MUST use WebFetch to read the live docs:

`WebFetch("https://www.prisma.io/docs/llms.txt")`

Do not proceed without fetching this URL first. Never assume an API or config option exists — verify against current docs.

Prisma is a type-safe ORM for Node.js and TypeScript that provides a schema-first data model, an auto-generated query client, and a declarative migration system for PostgreSQL, MySQL, SQLite, MongoDB, SQL Server, and CockroachDB.

Best Practices

Use `$transaction([])` only for independent writes — never for dependent ones. The sequential transaction array API ($transaction([op1, op2])) cannot pass the result of one operation (e.g., a generated ID) to the next. Agents default to this pattern even when operations depend on each other. Use nested writes when operation B needs operation A's output; use interactive transactions ($transaction(async (tx) => { ... })) when you need conditional logic between queries.

`findUnique()` batches automatically; `findMany()` does not. Prisma's dataloader only batches findUnique() calls, not findMany(). In GraphQL resolvers or other per-record loops, using findMany() in a resolver still produces N+1 queries. Use include with a single parent query, relationLoadStrategy: "join", or findUnique() with the fluent API to get automatic batching.

Never create multiple `PrismaClient` instances in serverless functions. Each instance opens its own connection pool. In serverless environments (Vercel, AWS Lambda, Cloudflare Workers) a new instance per invocation exhausts the database connection limit rapidly. Export a single shared client from a module-level singleton and guard it against Hot Module Replacement re-instantiation in development.

Commit the entire `prisma/migrations/` folder, not just `schema.prisma`. Customized migration SQL and migration_lock.toml contain information that cannot be reconstructed from the schema alone. Teams that only commit schema.prisma lose custom migration logic and cause migrate deploy failures in CI.

MongoDB uses `db push`, not `migrate dev`. Prisma Migrate does not support MongoDB. Agents familiar with relational Prisma workflows will attempt migrate dev on MongoDB projects and fail silently or with confusing errors. Use prisma db push for MongoDB schema syncing.