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Read Replicas

Configure read replicas for database scaling.

Overview​

Read replicas offload read queries from the primary database, improving performance for read-heavy workloads.

PostgreSQL Streaming Replication​

Primary Configuration​

# postgresql.conf
wal_level = replica
max_wal_senders = 5
wal_keep_size = '1GB'

Replica Configuration​

# Create replica from primary
pg_basebackup -h primary-host -D /var/lib/postgresql/data -U replication -P

# recovery.conf (or standby.signal in PG12+)
primary_conninfo = 'host=primary-host port=5432 user=replication password=secret'

TypeORM Configuration​

// ormconfig.ts
{
  type: 'postgres',
  replication: {
    master: {
      host: process.env.DB_HOST,
      port: 5432,
      username: process.env.DB_USER,
      password: process.env.DB_PASS,
      database: process.env.DB_NAME,
    },
    slaves: [
      {
        host: process.env.DB_REPLICA_HOST,
        port: 5432,
        username: process.env.DB_USER,
        password: process.env.DB_PASS,
        database: process.env.DB_NAME,
      },
    ],
  },
}

Query Routing​

TypeORM automatically routes:

  • Writes (INSERT, UPDATE, DELETE) β†’ Primary
  • Reads (SELECT) β†’ Replicas (round-robin)