Engineering notes
How things actually work — the mechanism, the defaults, and what they cost you. Written against primary sources and reviewed before publishing.
Microservices Interview Questions, Answered by Running Them
Seven microservices interview questions answered with counts from running Spring Boot services — starting with why three retries at three hops made 64 calls.
Distributed SystemsSQL Interview Questions for Experienced Engineers, Settled on Two Real Databases
The SQL questions experienced engineers get, run on PostgreSQL 17 and MySQL 8.4 — including a REPEATABLE READ that silently lost an update on one of them.
DatabasesJava Multithreading Interview Questions, Answered by Running Them
Six questions from every Java concurrency interview, answered with a program's output rather than a definition — starting with how much a race really loses.
JavaA GitHub Actions Pipeline, With the Seconds Attached
A workflow that really runs, quoted as it is, with the per-step timings from a real run — where 84 seconds go, what caching buys, and the two lines that matter.
Cloud & DevOpsDocker Compose and Spring Boot: Let the Application Start the Database
Spring Boot can drive Docker Compose itself — verified with the log where it waits for the container to go healthy, in a project holding no datasource config.
ContainersA Spring Boot Microservices Example, and the 22 Seconds Nobody Shows You
Two services, one HTTP call, measured — including what the caller does when the other service is stopped, and when it is merely slow.
Distributed SystemsSpring Boot Logging: JSON Is One Property, and the Guard You Still Need
Structured logs without a logback file or an extra dependency, MDC keys as real JSON fields, and a measurement correcting what you were told about placeholders.
Cloud & DevOpsSpring Boot Actuator: Only One Endpoint Is On By Default
What Actuator actually exposes on a fresh application, why /actuator/info comes back empty, and the endpoint that changes a log level without a restart.
Cloud & DevOpsSpring Boot Pagination and Sorting, and the Page You Should Not Return
Pageable and Page in two lines — then the runtime warning Spring Data logs about returning Page from a controller, and the COUNT query every page costs.
Backend & APIs