01 July 2014

Tidbits about the WoW backend

This discussion with Joe Rumsey, a software engineer for World of Warcraft at Blizzard, took place in 2013, but I'm only posting about it now.

  • Their database has 50% read and 50% write. There used to be more writes because the durability of player's equipment used to decrease often in combat. They have a proxy in front of the DB. The proxy flushes to DB periodically. Around 20 shards per DB. Transactions: inventory, trade, zone change, but not combat/monsters state.
  • 800-meter zones. Sort of dynamic zone borders. Would rather have one big zone on one server than two zones with a lot of exchange between them on different servers. Objects are mirrored on adjacent zones. If a zone falls, the entire server falls. To move an entity between two servers, server 1 flushes the entity to DB then server 2 retrieves it from DB; the two servers never exchange the player data.
  • The game server ticks at 2.5 times per second.
  • The clients connect to a proxy.
  • JSON vs binary messages: JSON's performance is fine 95% of the time.