Twitter services that are publicly exposed have seen a global latency average has racked on 150ms with regular spikes of several seconds or more. [1]
Core services for Twitter have been throwing 500s a dozen times every few hours. [2]
Twitter performance for users in Australia has fallen apart twice due to what was found out to be someone losing access to a root certificate and mitigation delayed because the team that could fix it is no longer employed. [3]