> Latency is additive; it's a sum() operation, not a max() operation. This! And you can only discard some components latency when it disappears in the deviatio

> Latency is additive; it's a sum() operation, not a max() operation. This! And you can only discard some components latency when it disappears in the deviation of another components much larger latency. In most PHP (or Ruby/Python/etc for that matter), this is not the case. They add some 10-150ms on top, and often the db calls are <10ms. Performance does matter, and is hard to improve once you have many KLOC of code in a slow language. Hence FB spend big bucks on PHP performance improvements.