[mdoms]

Incredibly ignorant statement. An activity can have thousands of data points across dozens of metrics. A record of your route to 1 meter or smaller precision for a 5 hour bike ride is alone thousands of data points. Along with hundreds or thousands of time series points for heart rate, elevation, cadence, power, respiration, etc etc... Millions of activities means tracking tens of billions of data points and perhaps an order of magnitude more than that.

[mulmen]

There’s no reason all that granular data would be used to calculate a leaderboard. It can be rolled up in advance and for leaderboard purposes most of it can be ignored.

Parallelism along the location, customer and activity dimensions makes this an easily reducible problem.