Jaana Dogan started with a draft and this tweet and ended up laying down some serious knowledge on databases.
A large majority of computer systems have some state and are likely to depend on a storage system. My knowledge on databases accumulated over time, but along the way our design mistakes caused data loss and outages. In data-heavy systems, databases are at the core of system design goals and tradeoffs. Even though it is impossible to ignore how databases work, the problems that application developers foresee and experience will often be just the tip of the iceberg.