Recently, researchers at UC Berkeley published TAOBench, an end-to-end benchmark for social network workloads based on the traces collected from TAO, the distributed database for Meta. Among the typical data operations in social network applications, 99.7% are read, while only 0.2% are write and 0.01% are write transactions. Some other findings include:

Transaction hotkeys are often co-located.
Read and write hotspots appear on different keys.
Contention can result intentionally.

All these characteristics of social network application workloads pose special challenges.