I have database replicas. Do I still need backups?

Yes. A replica applies every write within seconds, including the accidental DROP TABLE, the ransomware encryption, and the application bug corrupting rows. Replication protects against hardware failure; only backups with point-in-time recovery let you rewind to before a mistake. Treat them as answers to different disasters, because they are.

How do I actually pick RTO and RPO values?

Price the outage with the business: revenue per hour of downtime, cost and legal exposure of losing an hour of data. Then price the tiers of protection and put the two numbers side by side. The right RTO and RPO are where those curves cross, and they will differ per system, which is why blanket company-wide targets usually mean overspending somewhere and gambling somewhere else.

Is multi-region active-active overkill?

For most companies, yes. Full region outages are rare, and active-active roughly doubles infrastructure cost while forcing hard consistency decisions onto every write path. Pilot light or warm standby captures most of the protection at a fraction of the cost and complexity. Go active-active when the revenue math genuinely demands near-zero RTO, not for the architecture diagram.

Reliabilitychapter 3 of 5 · 3 lessons

Disaster Recovery

Plan for full region failure. RTO and RPO define how fast and how much data you can afford to lose.

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At 11:20 an engineer runs a cleanup script against the wrong environment and drops the production database.

Your replicas do not save you. They applied that delete faithfully within a second, all three of them, because that is their entire job.

What saves you is a backup taken before 11:20, and the answer to two questions nobody has asked yet: how long until people can use the site again, and how much of this morning's data are you about to lose forever.

Both are numbers, both belong to your business rather than to you, and the worst time to discover them is now.

Lessons

3 in this chapter

RTO and RPOTwo numbers the business picks and engineering prices: how long down, how much data gone.3 min
Backups That Actually RestoreNobody wants backups; everybody wants restores. Only one of those gets tested by default.3 min
DR Architectures by BudgetFour standard tiers, each buying a better RTO with a bigger bill.3 min