Rearchitecting GitHub Pages (2015)

8 days ago

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GitHub Pages initially ran on a single pair of machines with a simple architecture.
The old system had limitations like 30-minute delays for new sites and storage constraints.
The new architecture includes a frontend tier with nginx and ngx_lua for routing, and a fileserver tier with DRBD for data replication.
MySQL read replicas are used for routing, with mitigations for availability issues.
Fastly caches responses to minimize downtime impact.
The new system allows instant publishing of new sites and horizontal scaling of storage.
ngx_lua's performance is excellent, adding less than 3ms to requests at the 98th percentile.

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