Backups, Point-in-Time Recovery, and Restore Drills

A PostgreSQL backup is useful only if it can restore the required data within the declared recovery point and recovery time. Logical dumps reconstruct selected objects; physical base backups plus archived WAL enable cluster recovery and point-in-time recovery. Retention, encryption, access, version compatibility, dependencies, and isolated restore drills complete the system.

What will you be able to do?

• Translate RPO/RTO into backup and WAL requirements.
• Compare pg_dump/pg_restore with physical backup and PITR.
• Design encrypted, immutable, monitored retention.
• Run a restore drill with application-level validation.

Prerequisites and mental model

RPO asks how much committed data loss is acceptable; RTO asks how long service restoration may take. A backup file, a replica, and WAL archive are different capabilities.

Which backup serves which need?

• pg_dump creates a logical, transactionally consistent export of one database and is useful for selective restore/migration; it is not continuous PITR.
• Physical backups copy cluster files in a supported way and pair with WAL for recovery.
• WAL archiving preserves the change stream needed to replay from a base backup to a target.
• Managed services expose provider-specific snapshots/PITR with limits that must be tested.

Safe logical learning example:

Restore into a newly created isolated database, never over the source during practice. Use current-version tools and official compatibility guidance.

What proves recovery?

Record:

1. backup identity, checksum, encryption, location, and retention;
2. restore start/end and exact target;
3. database/version/extension prerequisites;
4. row-count and invariant checks;
5. roles/grants/RLS/function verification;
6. application smoke and tenant-negative tests;
7. RPO reached and RTO measured;
8. issues and runbook changes.

Why does this matter in AI-native systems?

Restore canonical documents, access policy, evaluation cases, approvals, and audit history first. Embeddings may be rebuilt, but only when source/version/model lineage exists and rebuild time fits RTO. External object storage and model-provider state need coordinated recovery plans.

Prove it worked

Dump signaldesk_learning, restore into signaldesk_restore_drill, run invariant/role/RLS checks, compare selected counts/checksums, and then remove only the explicitly named drill database when finished. Record elapsed time.

Production judgment

• Test expired credentials, missing extensions, and unavailable key scenarios.
• Keep copies outside the primary failure/credential domain and use immutability where justified.
• Backup monitoring must detect silent gaps and WAL archive failure.
• Logical dumps can be slow/large and do not capture cluster-wide configuration/roles automatically in the same way.

Common mistakes

• Backup job green, restore fails: no drill → schedule isolated restores.
• PITR gap: WAL archive missing → monitor continuity and restore test.
• RAG restored without sources: embeddings treated as truth → preserve source and lineage.

AI Pair-Programmer Prompt

Hands-on exercise

Perform the isolated logical restore drill and write a one-page evidence report.

Acceptance criterion: restored SignalDesk passes schema, count, constraint, role, tenant-negative, and application-query checks within measured time.

Knowledge check

1. What enables PITR?
2. Is a replica a backup?
3. What makes embeddings safely rebuildable after restore?

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Answers

1. A suitable physical/base backup plus continuous required WAL and recovery configuration.
2. No; it shares/replays many failures and lacks independent history.
3. Restored canonical sources, versions, pipeline/model identity, and rebuild procedure/capacity.

Completion checklist

• RPO and RTO are explicit.
• Backup type matches recovery need.
• Restore is isolated and evidence-based.
• External and derived data recovery is included.

Primary references

• Backup and restore
• pg_dump
• pg_restore
• Continuous archiving and PITR