Migrating to an Event Sourced system
summary
Real estate app experiments with event sourcing but stops short of full migration: backend remains PostgreSQL while teams prototype an event log, try Elixir + Phoenix + Absinthe (GraphQL), adopt commanded CQRS library (pre-1.0), and convert numeric IDs to UUIDs to generate commands outside the DB. Tests and coexistence of old relational repo plus event repo prove painful, many features balloon to dozens of files and hundreds of lines, eventual consistency and aggregate modelling cause surprises, and outcome is a partial proof-of-concept that teaches DDD, event storming and where to apply event sourcing later.
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