Java / Spring — Engineering Journal

Jul 06, 20268 min

The Failover That the JVM Slept Through: A DNS Record Nobody Re-Resolved

A database failover completed in under a minute. DNS flipped the endpoint to the new primary's address almost immediately, every other service reconnected, and the incident should have been over. One Java service kept hammering the old, now demoted, host for the better part of an hour. It was not a bug in our code or a slow health check. The JVM had resolved that hostname once at startup and cached the IP address effectively forever.

JavaDNS

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Java / Spring

May 17, 202611 min

Java Concurrency and the Memory Model

Visibility, atomicity, and happens-before are three different guarantees, and most concurrency bugs come from confusing them.

concurrencyjvm

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Java / Spring

May 14, 202610 min

@Transactional: The Pitfalls Nobody Warns You About

@Transactional is a proxy, not a keyword — and that one fact explains self-invocation, silent commits on checked exceptions, and most production data bugs.

SpringTransactions

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Java / Spring

May 12, 202610 min

The N+1 Problem and the Hibernate Persistence Context

The N+1 problem is a leak in Hibernate's lazy-loading abstraction; understanding the persistence context and entity lifecycle is what lets you fix it deliberately rather than by trial and error.

HibernateJPA

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Java / Spring

May 10, 202610 min