# Sre
All Sre notes →1 — Designing Planet-Scale Systems
What changes architecturally once a system has to serve every region on earth — the assumptions that hold at one datacenter's scale and break at planet scale.
2 — Global Traffic Management
Routing users to the right region by latency, health, and capacity simultaneously, and the DNS- and anycast-level mechanics that make global failover fast.
3 — Edge Computing
Pushing compute and data closer to the user to cut latency, and the consistency and deployment complexity that distributing logic to the edge buys in exchange.
4 — Multi-Cloud Reliability
The real cost — not just financial — of running reliably across more than one cloud provider, and where multi-cloud actually reduces blast radius versus just adding complexity.
5 — Active-Active Systems
Serving live traffic from more than one region simultaneously, and the conflict-resolution problem that active-active pushes onto every stateful write.
6 — Active-Passive Systems
Keeping a standby ready to take over, and the failover-testing discipline that's the only thing standing between 'passive' and 'silently broken.'
7 — Disaster Recovery Patterns
The concrete architectural patterns — pilot light, warm standby, multi-site — that turn a DR strategy from a document into something that actually executes under pressure.
8 — Cost vs Reliability
Why every nine of additional availability has a real, escalating price tag, and the point past which more redundancy stops being worth what it costs.
9 — Sustainability Engineering
Carbon and energy footprint as an emerging constraint on architecture decisions, alongside cost and reliability rather than instead of them.