[rich_archbold]

At the time we made the decision, we had a very small number of Postgres DB's in production and a large number of MySQL DB's in production.

We had built up a LOT of excellent operational tooling and expertise to enable us to operate MySQL to a really high standard and didn't have the same tooling/knowledge in place for Postgres.

Also, the Postgres instances were not chosen for any specific, differentiating Postgres features, more because the original developer preferred Postgres to MySQL.

We had recently encountered a few completely avoidable Postgres outages, mainly arising from the fact that they were not covered by the same level of supporting operational tooling that our MySQL DB's had.

We were faced with 2 choices: 1. spend a bunch of time leveling up our tooling and knowledge around Postgres 2. standardize on MySQL and migrate the small number of Postgres instances to MySQL

We chose option 2. And believe it provided the right level of improved operability at the lowest cost.

The icing on the cake was that soon after, AWS Aurora was launched with MySQL-only support (later they did also launch Postgres support for Aurora) which allowed us to get a 5X throughput improvement at a 30% cost reduction. These numbers were not just AWS marketing numbers, we benchmarked them with our workloads and found them to be true.