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Chapter 1 · Designing scalable, highly available databases·v1.0.0·Updated 6/15/2026·~16 min

What's changed: Created Professional Cloud Database Engineer Chapter 1 (Domain 1 "Design": capacity and HA/DR = workload metrics/perf-cost/zonal-regional-multi-regional/maintenance windows/RTO-RPO-PITR; connectivity/access and DB choice = Cloud SQL Auth Proxy/private IP/CMEK/session poolers/audit, Cloud SQL/AlloyDB (vector/gen AI)/Spanner/Bigtable/Firestore, managed/SQL/NoSQL/vector).

1.1Capacity planning and HA/DR design

Key points

Understand database capacity/usage planning from current workload metrics and future requirements, performance/cost tradeoffs, multi-regional/regional/zonal deployment strategies, maintenance windows, and designing high availability and disaster recovery to meet RTO/RPO/PITR.

A Professional Cloud Database Engineer translates business/technical requirements into scalable, resilient, cost-effective databases. Design starts with capacity planning and availability/disaster recovery.

1.1.1Capacity planning and performance/cost

Capacity planning sizes database compute and storage from current workload metrics (CPU/memory/IOPS/connections) and future requirements. Evaluate the performance/cost tradeoff (machine type, storage type) to avoid over- or under-provisioning. Map "size from current + future" and "balance performance against cost."

1.1.2High availability and DR (RTO/RPO/PITR)

Availability comes from placement: zonal (single zone, weak) → regional (multi-zone, tolerates zone failure) → multi-regional (tolerates regional failure). Design DR by RTO (recovery time) and RPO (acceptable data loss), with PITR (point-in-time recovery) to roll back to a specific moment. Set maintenance windows to match availability requirements. Map "tolerate zone failure = regional (HA)" and "recover to a point in time = PITR."

Exam point

Common: requirement → design. E.g., "DB tolerant to zone failure" = regional (HA); "tolerate regional failure" = multi-regional; "roll back to before a bad change" = PITR; "acceptable data loss/recovery time" = RPO/RTO; "size from current + future" = capacity planning from workload metrics; "fit downtime to availability" = maintenance windows.

Warning

Watch the mix-ups: (1) Do not confuse RTO (time), RPO (data loss), and PITR (point-in-time recovery). (2) Availability comes from placement spread (zonal is weak). (3) Size capacity for future requirements, not just current.

Diagram of capacity planning from workload metrics with performance/cost, availability zonal<regional<multi-regional, and RTO/RPO/PITR with maintenance windows.
Design size and availability

1.1.3Section summary

  • Capacity planning = size compute/storage from current metrics + future; evaluate performance/cost
  • Availability = zonal < regional (HA) < multi-regional
  • Design DR by RTO/RPO with PITR; fit maintenance windows to availability

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Quick check

(just a quick review)

Q1. To make a database resilient to zone failure, which placement best fits?

Q2. To roll back a database to a specific point before a bad change/corruption, which feature?

Q3. Which correctly contrasts RTO and RPO?

Q4. What is the best approach to database capacity planning?

Q5. You need the highest availability tolerating a whole-region failure. Which placement?

Q6. To control planned downtime to match app availability requirements, what do you set?

Check your understandingPractice questions for Chapter 1: Designing scalable, highly available databases