PostgreSQL

A single-node PostgreSQL container. Defaults to a test/test/test user/password/database trio so connectionString is usable with zero configuration.

Default image: postgres:18-alpineExposed port: 5432Wait strategy: log message "database system is ready to accept connections", twice

Member	Returns
PostgresContainer.start(image?)	Promise<PostgresContainer> — boots the container
.withUsername(name)	this — overrides POSTGRES_USER (default test)
.withPassword(pw)	this — overrides POSTGRES_PASSWORD (default test)
.withDatabase(name)	this — overrides POSTGRES_DB (default test)
.username / .password / .databaseName	The configured values
.connectionString	A postgres://user:pass@host:port/db connection string

Example

import { PostgresContainer } from "rightsize/modules";
import pg from "pg";

await using postgres = await PostgresContainer.start();
const client = new pg.Client({ connectionString: postgres.connectionString });
await client.connect();
await client.query("CREATE TABLE t (x INT)");
await client.query("INSERT INTO t VALUES (1)");
console.log((await client.query("SELECT * FROM t")).rows);
await client.end();

Backend notes

• Why the wait strategy counts to two, not one. The official entrypoint boots the server once to run init scripts, shuts it down, then starts it again for real — printing the readiness line both times. Waiting for the first occurrence races that restart: a client can connect to the init-time server moments before it's torn down. This module's times: 2 wait is the fix, and the reason Wait.forLogMessage's times parameter exists at all — see Wait strategies.
• A microsandbox-only environment-variable fix, harmless on Docker. The official postgres:*-alpine image bakes an environment variable (DOCKER_PG_LLVM_DEPS) containing a literal tab character, which crashes microsandbox's VM builder before the guest ever boots. This module clears that variable by default — invisible on Docker, required on microsandbox. Nothing you need to do.