A beginner Spring Boot project should force you to make decisions: entities, APIs, auth, errors and a UI consumer. Cognitex uses three shapes that scale into interview stories.
1. E-commerce slice
Catalog, cart, orders, admin. You will hit SQL design, statuses, and “who can call this endpoint?”
2. Internal tool (hospital / HR / inventory)
Roles, JWT, audit-ish history. Messy real-world rules beat another public REST demo.
3. AI support assistant
Retrieve from your own documents, call an LLM, show answers in Angular or React, and write tests for “I don’t know.”
Definition of done
README, diagram, sample requests, tests for the core path, Git history, and a deploy. That is the difference between a course exercise and engineering.