Build the Query Performance Analyzer first. It solves a real problem you have today -- slow queries in production that you diagnose with ad hoc EXPLAIN ANALYZE runs and gut instinct -- and turns it into a systematic tool. More importantly, it demonstrates deep PostgreSQL knowledge in interviews. When someone asks "tell me about a project that shows your database skills," you do not want to say "I added indexes." You want to say "I built a tool that monitors query plans, detects regressions, and suggests optimizations." That is a different conversation entirely.
The event-sourced feature is where databases and architecture intersect. Event sourcing is not just an architectural pattern -- it is a database design challenge. Your event store needs append-only writes, efficient range queries by aggregate ID, and snapshots to avoid replaying thousands of events. Building this in PostgreSQL rather than reaching for a specialized event store proves you understand your database deeply enough to push its boundaries. It also gives you firsthand experience with the tradeoffs: storage growth, projection rebuilds, eventual consistency. Theory becomes visceral when you watch your event table hit ten million rows.
This curriculum -- all eight modules plus this capstone -- has the highest career ROI of any path in the program. I say that without hesitation. Database knowledge is the number one differentiator in Rails interviews. Senior-role rejections often trace back to database-related gaps. Every "how would you scale this" question is secretly a database question. Every "tell me about a production incident" story worth telling involves a database. Every staff-level architecture discussion assumes you understand data modeling, query performance, and replication. This curriculum does not just fill gaps. It builds the foundation that makes everything else click.