- Hasura – Remote Schemas and Federation
Stitching an existing GraphQL API into Hasura's schema so clients see one graph instead of two. Adding a remote schema, the namespacing and type-collision problems that follow, remote relationships that join a database row to a field on another service, and how permissions and header forwarding work across the boundary. Then v3, where this stops being a bolt-on and becomes what the supergraph is.
- Java 17 Sealed Classes
A sealed type declares exactly which types may extend it. The compiler enforces the list, and — this is the real payoff — it can then prove that a switch over that type has covered every case. The problem An ordinary interface is open: anyone, anywhere, can implement it. That is usually the point.…
- Recursion
A method that calls itself on a smaller version of the same problem. The base case and the progress towards it, what the call stack is really doing, why StackOverflowError is a message rather than a mystery, and when a loop is the better answer.
- Spring Boot – Elasticsearch
Full-text search that a LIKE query cannot do. Spring Data Elasticsearch repositories, mapping a document, keeping the index in step with the database, and being honest about the operational cost — this is the point where the demo app stops needing only MySQL.
- Python – Lambda Functions
The one-expression anonymous function. Where it belongs — a sort key, a small callback — where it does not, and why `sorted(xs, key=lambda p: p.name)` is the example that justifies the whole feature.