Start from

OR A BRIEF

• warm-upThree servers and a load balancerOne app, three servers, nothing clever. Four components are the whole answer.
• cachingProduct pages at lunchtimeTwo thousand reads a second of things that change a few times a day, and a database at 90%.
• replicationReads that outgrew one databaseSix thousand reads a second and two hundred writes on one box, and an editor who must see their own save.
• asyncPhoto recognition behind a slow vendorA vendor that takes three to seven minutes, offers no callback, and fails two per cent of the time.
• consistencyTwo hundred seats, five thousand buyersTwo hundred seats, five thousand buyers in the same two seconds, and a payment provider that takes its time.
• reliabilityWebhooks that will not stop arrivingTwo seconds to answer, five retries, and the same event arriving twice.