Prisma 'PrismaClientInitializationError: Can't reach database server at `host`:`port`' (P1001) - how do I fix it?

Cause: Prisma could not open a connection to the host and port in your connection URL. Typical reasons: the database is not running or not listening on that address, the host name is wrong from where the code runs (for example localhost inside a Docker container points to the container itself), a firewall or security group blocks the port, the DATABASE_URL variable is missing or points somewhere else, or the URL has unescaped special characters. PrismaClientInitializationError is the class thrown when the client starts and connects (on $connect() or the first query); related codes are P1000 (authentication failed), P1002 (timed out) and P1017 (server closed the connection). Fix (best first): 1. Print the host and port from the effective DATABASE_URL (without the password) and confirm they are what you expect in the environment where the error occurs. Check the .env file is loaded and that CI or production sets the variable. 2. Test reachability from the same machine or container with a database client or a TCP check, and make sure the database process is up and bound to a reachable interface. 3. In Docker or Compose, use the service name as host (for example db) rather than localhost, put both containers on the same network, and wait for the database to be ready before starting the app (a healthcheck plus depends_on condition). 4. Percent-encode special characters in the user name or password, as in p@$$w0rd written as p%40%24%24w0rd. Prisma requires this for PostgreSQL, MySQL and CockroachDB URLs. 5. Open the port to the app only (security group, firewall, VPC rule). Do not open the database to the whole internet to make the error go away. 6. For P1002 or intermittent failures with managed or serverless databases, check that the instance is awake and the provider's connection limits are not exhausted; retry logic helps. 7. Other documented causes of this error class: invalid credentials, an inaccessible environment variable, or the query engine binary missing for the platform. Verify: run npx prisma db pull or a trivial query such as prisma.$queryRaw with a harmless select 1 from the same environment; it should succeed. Sources: https://www.prisma.io/docs/v6/orm/reference/error-reference https://www.prisma.io/docs/v6/orm/reference/connection-urls