6 posts · 17 topics

Backend notes, written after the fix.

Auth, event delivery, query performance, and how to lay a service out so the next person can change it safely. Mostly things that bit me in production first — written the way I'd explain them to whoever inherits the code, not the way a tutorial would.

Shipping the Same Spring Boot Service to AWS and GCP

The container is the portable part. Everything around it — queues, secrets, identity, database connections — is not. What actually differs between the two, and which differences are worth abstracting away.

AWSGCPCloudSpring Boot

22 Jul 202610 min

JWT Authentication in Spring Boot, End to End

What is actually inside a JWT, why the signature is the only part that matters, and how to issue, validate and rotate tokens in Spring Security 6 without building a session store by accident.

JWTSpring SecurityAuth

14 Jun 202611 min

Keycloak and Spring Security: Stop Writing Auth Filters

Most Keycloak integrations carry hundreds of lines of custom filter code that Spring Security already does better. Here is the small correct configuration, plus how roles, scopes and service-to-service calls actually fit together.

KeycloakOAuth 2.0Spring SecurityAuth

2 May 20269 min

Idempotent Kafka Consumers: Exactly-Once in Practice

Kafka gives you at-least-once by default, which means duplicates are not an edge case — they are the contract. How to build consumers that can be redelivered the same message twice and not charge anyone twice.

KafkaDistributed SystemsSpring Boot

21 Mar 202610 min

Killing the N+1 Query in Spring Data JPA

The endpoint that ran fine with twenty rows and fell over with two thousand. How to find N+1 queries, the four ways to fix them, and why the obvious fix quietly breaks pagination.

JPAHibernatePerformancePostgreSQL

8 Feb 20269 min

How I Structure a Spring Boot Microservice

Package by feature, keep the domain free of Spring, and put every boundary concern in one place. The layout I have converged on after a few services that were painful to change.

Spring BootArchitectureMicroservices

11 Dec 20258 min