Re:Introducing Cloud Spanner, a Global Database Service
by dekhn on Tuesday February 14, 2017 @06:03PM
(#13648136)
I don't know why you think MDB is ginormous by MySQL standards; it was actually quite modest.
Everything you need to know is here: https://research.google.com/pubs/pub38125.html
it walks through the architecture of the Ads DB, the issues with replacing MySQL, and some of the heroic efforts to implement it via Spanner.
At the time, I asked the team why they used MySQL instead of Postgres (which I prefer) and the short answer was: MySQL replication worked at the time.
I don't know if anyone put it to them that way but as Spanner was just getting started when I left I know that one of its success criteria was to be able to be a scalable replacement for MDB. Given the white paper and other papers on their results, I'm sure it managed that requirement.
[1] MDB, Machine Data Base, used throughout the org but especially in Platforms and SRE to keep track of machines and their parts.