<Designing Data-Intensive Applications: The Big Ideas Behind Reliable, Scalable, and Maintainable Systems> Everything changes and nothing stands still. —Heraclitus of Ephesus, as quoted by Plato in Cratylus (360 BCE) Applications inevitably change over time..  schema-on-read (“schemaless”) databases don’t enforce a schema, so the database can contain a mixture of older and newer data formats written…