Java, Spring Framework & Spring Boot

createdAt, updatedAt and createdBy without manual code.

Cache expensive reads with one annotation.

Every request passes through a chain of filters before your controller.

Stateless API auth with signed tokens, the Spring way.

Never store passwords — store slow, salted hashes.

Authorize at the service layer, not just URLs.

Most CORS errors are configuration mistakes.

Social login with a few lines of config.

Validate tokens from any OIDC provider.

Actuator can leak secrets if exposed carelessly.

Fast tests for business rules without starting Spring.

Assertions that read like sentences and fail clearly.

Test the HTTP layer — routing, validation, JSON — in milliseconds.

Test against the real database engine, not H2.

Prove the whole app works together.

Readable tests start with readable setup.

Catch breaking API changes before consumers do.

Coverage is a flashlight, not a target.

Find tests that pass no matter what the code does.

Security bugs are the ones you cannot afford.

Microservices solve organizational problems — and create technical ones.

One entry point for routing, auth and rate limiting.

Config across many services without drift.

Produce and consume events with Spring for Apache Kafka.

Work queues and routing with AMQP.

Follow one request across every service.

Stop hammering a dependency that is already down.

Keep data consistent across services without distributed transactions.

At-least-once delivery means duplicates. Plan for them.

@Scheduled is easy. Running it on many instances is not.

Small, fast-starting images with layered jars.

Production images without writing a Dockerfile.

Millisecond startup and tiny memory — with trade-offs.

Let the JVM size itself from container limits.

Three good options and when to pick each.

Build, test and publish on every push.

Deploys should not drop in-flight requests.

Slow startups hurt deploys, tests and autoscaling.

Low-overhead profiling you can run in production.

Dashboards that tell you when something is wrong.

What interviewers ask — and what a strong answer includes.

Common questions and the answers that show real experience.

The most common Spring startup error, explained.

Lazy collections accessed after the session closed.

Spring Boot forbids them by default — and that is good.

Keep the framework at the edges of your code.

Microservice boundaries without microservice costs.

Both are first-class. Choose by team, not hype.

What to learn, in order, to become productive.

The lessons that matter most from the whole series.