Databases

Databases and caches available to every environment

Every environment comes with a MongoDB database, and an app can declare managed PostgreSQL databases and Redis caches next to its service. All of them are created in the environment’s region, reach the app through environment variables, and are backed up in production.

MongoDB

Each environment gets its own MongoDB database with nothing to declare. Its connection string is in MONGODB_URI and MONGO_URL. Apps built on the Modelence framework use it without any setup.

PostgreSQL and Redis

Managed databases and caches are declared in the resources section of modelence.config.json, and the app reads each one through a variable tied to one of its outputs:

modelence.config.json

{
  "resources": {
    "api": {
      "type": "service",
      "build": { "commands": ["npm ci"] },
      "start": { "commands": ["node server.js"] }
    },
    "main-db": { "type": "postgres", "plan": "postgres-1gb" },
    "cache": { "type": "redis" }
  },
  "env": {
    "DATABASE_URL": { "type": "resource", "resource": "main-db", "output": "url" },
    "REDIS_URL": { "type": "resource", "resource": "cache", "output": "url" }
  }
}

The url output is a full connection string, postgresql://...?sslmode=require for PostgreSQL and rediss://... (TLS) for Redis. The other outputs are its parts, for clients that read them separately. The reference lists every plan and output.

Managed resources need a paid plan.

Lifecycle

A deploy creates every managed resource the file declares that the environment doesn’t have yet, and the new version starts only once they are ready. Resources are matched by name, so the same file works in every environment:

• A resource that already exists is kept as it is, with its data. plan is read only when the resource is created, so changing it later has no effect.
• A resource removed from the file is not deleted, and it is billed until it is.
• Renaming a resource creates a new, empty one, and the old one stays until it is deleted.

Deleting a managed resource permanently deletes its data and its backups.

Databases hosted elsewhere

An app can also use a database hosted somewhere else, such as Supabase, Neon or PlanetScale. Keep its connection code and declare its URL and keys in env as secrets.