[swah]

tl;dr but so the simple operations like "update my birthdate" happen with sync MySQL operations?

[luhn]

Yep. All their applications always write directly to MySQL.

[happyslobro]

I guess if that became a bottleneck, they could set up a queue for write requests. Maybe even something more sophisticated that automatically batches similar writes that pile up in the queue. They could use something like Kafka for this...