The document discusses problems with traditional mutable databases like losing history data when records are updated and the inability to retrieve past states. It introduces Datomic as an immutable database that can retrieve past states using its "as-of" operator similar to a git checkout. It also explains that Datomic improves scalability by running queries on clients instead of the server and uses transactions through data forms instead of SQL to prevent injection attacks. Workarounds without Datomic include using as-of in SQL 2011, Kafka with CQRS/event sourcing, or wrapping SQL in APIs. Overall, Datomic provides lessons on separating reaction from perception and solving impedance mismatch through an alternative approach of decomposing databases.