https://github.com/facebookincubator/beringei
Each system and service at Facebook writes hundreds to thousands of counters to our storage engine, and this data is available to query in real time by engineers looking at dashboards and doing ad-hoc performance analysis.
Beringei currently stores up to 10 billion unique time series and serves 18 million queries per minute, powering most of the performance and health monitoring at Facebook while enabling our engineers and analysts to make decisions quickly with accurate, real-time data.