RDS Basics

RDS runs a managed relational database — the same Postgres or MySQL engine you’d run yourself, minus patching, backups, and failover, which AWS handles. This lesson launches one, connects to it, and rehearses the snapshot/restore workflow you hope never to need in a hurry.

This lesson uses a real AWS free-tier account. LocalStack’s open-source edition registers RDS instance metadata but does not run a real, connectable Postgres engine or support snapshot/restore — that is a Pro-tier feature. A db.t3.micro Single-AZ instance is within the RDS Free Tier.

Launching an instance

aws rds create-db-instance \
  --db-instance-identifier bookshop-db \
  --db-instance-class db.t3.micro \
  --engine postgres --engine-version 16.3 \
  --master-username dbadmin --master-user-password 'ChangeMe123!' \
  --allocated-storage 20 \
  --query 'DBInstance.{Id:DBInstanceIdentifier,Status:DBInstanceStatus}'

$ aws rds create-db-instance ...
{
    "Id": "bookshop-db",
    "Status": "creating"
}

Creation is asynchronous — the CLI returns immediately with creating, and the instance isn’t usable yet.

aws rds wait db-instance-available --db-instance-identifier bookshop-db
echo "ready"

$ aws rds wait db-instance-available --db-instance-identifier bookshop-db
ready

wait db-instance-available polls every 30 seconds and returns once the status flips — this run took about six minutes.

aws rds describe-db-instances --db-instance-identifier bookshop-db \
  --query 'DBInstances[0].{Endpoint:Endpoint.Address,Port:Endpoint.Port,Status:DBInstanceStatus}'

{
    "Endpoint": "bookshop-db.c9k2mfg8h3rt.us-east-1.rds.amazonaws.com",
    "Port": 5432,
    "Status": "available"
}

Connecting

psql "host=bookshop-db.c9k2mfg8h3rt.us-east-1.rds.amazonaws.com \
      port=5432 dbname=postgres user=dbadmin password=ChangeMe123!"

$ psql "host=bookshop-db.c9k2mfg8h3rt.us-east-1.rds.amazonaws.com port=5432 dbname=postgres user=dbadmin password=ChangeMe123!"
psql (16.3)
SSL connection (protocol: TLSv1.3, cipher: TLS_AES_256_GCM_SHA384, compression: off)
Type "help" for help.

postgres=>

create table customers (id serial primary key, name text, country_code text);
insert into customers (name, country_code) values ('Ada Lovelace', 'GB'), ('Grace Hopper', 'US');
select * from customers;

postgres=> select * from customers;
 id |     name     | country_code
----+--------------+--------------
  1 | Ada Lovelace | GB
  2 | Grace Hopper | US
(2 rows)

If this connection instead hangs and times out, the cause is almost always the RDS security group not allowing inbound 5432 from wherever psql is running — the same default-deny model from the ec2 lesson applies here too.

Taking a snapshot

aws rds create-db-snapshot \
  --db-instance-identifier bookshop-db \
  --db-snapshot-identifier bookshop-db-before-migration \
  --query 'DBSnapshot.{Id:DBSnapshotIdentifier,Status:Status}'

{
    "Id": "bookshop-db-before-migration",
    "Status": "creating"
}

aws rds wait db-snapshot-available \
  --db-snapshot-identifier bookshop-db-before-migration
aws rds describe-db-snapshots --db-snapshot-identifier bookshop-db-before-migration \
  --query 'DBSnapshots[0].{Status:Status,Size:AllocatedStorage,Created:SnapshotCreateTime}'

{
    "Status": "available",
    "Size": 20,
    "Created": "2026-09-13T11:48:02.104000+00:00"
}

Simulating damage, then restoring

delete from customers;
select count(*) from customers;

postgres=> select count(*) from customers;
 count
-------
     0
(1 row)

aws rds restore-db-instance-from-db-snapshot \
  --db-instance-identifier bookshop-db-restored \
  --db-snapshot-identifier bookshop-db-before-migration \
  --db-instance-class db.t3.micro \
  --query 'DBInstance.{Id:DBInstanceIdentifier,Status:DBInstanceStatus}'

{
    "Id": "bookshop-db-restored",
    "Status": "creating"
}

aws rds wait db-instance-available --db-instance-identifier bookshop-db-restored
aws rds describe-db-instances --db-instance-identifier bookshop-db-restored \
  --query 'DBInstances[0].Endpoint.Address'

"bookshop-db-restored.c9k2mfg8h3rt.us-east-1.rds.amazonaws.com"

psql "host=bookshop-db-restored.c9k2mfg8h3rt.us-east-1.rds.amazonaws.com \
      port=5432 dbname=postgres user=dbadmin password=ChangeMe123!" \
  -c "select * from customers;"

 id |     name     | country_code
----+--------------+--------------
  1 | Ada Lovelace | GB
  2 | Grace Hopper | US
(2 rows)

A restore creates a new instance with a new endpoint — bookshop-db itself is untouched and still empty. An application pointed at the old endpoint would need its connection string updated to the restored one; nothing repoints it automatically.

Cleaning up

aws rds delete-db-instance --db-instance-identifier bookshop-db-restored --skip-final-snapshot
aws rds delete-db-instance --db-instance-identifier bookshop-db --skip-final-snapshot

{
    "DBInstance": {
        "DBInstanceIdentifier": "bookshop-db",
        "DBInstanceStatus": "deleting"
    }
}

--skip-final-snapshot avoids AWS silently taking one more (billed) snapshot on delete — appropriate here since a snapshot already exists, but leave it off in anything resembling production.

Practice

psql "host=bookshop-db.c9k2mfg8h3rt.us-east-1.rds.amazonaws.com port=5432 dbname=postgres user=dbadmin"

psql: error: connection to server at "bookshop-db.c9k2mfg8h3rt.us-east-1.rds.amazonaws.com" (10.0.1.42), port 5432 failed: Connection timed out

aws rds describe-db-snapshots --db-instance-identifier bookshop-db \
  --query 'sort_by(DBSnapshots, &SnapshotCreateTime)[].DBSnapshotIdentifier'

[
    "bookshop-db-before-migration",
    "rds:bookshop-db-2026-09-13-06-00"
]

aws rds describe-db-instances --db-instance-identifier bookshop-db \
  --query 'DBInstances[0].BackupRetentionPeriod'

7

aws rds modify-db-instance --db-instance-identifier bookshop-db \
  --multi-az --apply-immediately
aws rds wait db-instance-available --db-instance-identifier bookshop-db
aws rds describe-db-instances --db-instance-identifier bookshop-db \
  --query 'DBInstances[0].{MultiAZ:MultiAZ,AZ:AvailabilityZone,SecondaryAZ:SecondaryAvailabilityZone}'

{
    "MultiAZ": true,
    "AZ": "us-east-1a",
    "SecondaryAZ": "us-east-1b"
}

aws rds restore-db-instance-to-point-in-time \
  --source-db-instance-identifier bookshop-db \
  --target-db-instance-identifier bookshop-db-pitr \
  --restore-time 2026-09-13T11:40:00Z \
  --query 'DBInstance.DBInstanceIdentifier'

"bookshop-db-pitr"

Next: Lambda — writing, deploying, and invoking a function, and what cold starts actually cost.