Notes from building things that must not break.
Not tutorials. Things I learned the expensive way, written down so the next person — often future me — does not have to.
When Parallel Streams Become a Production Problem
parallelStream() is one call away and looks like free concurrency. On I/O-bound work sharing a JVM-wide pool, it is a way to make unrelated code slow.
Designing a Two-Level Cache with JCS and Redis
A local in-process cache in front of Redis buys latency and resilience. It bills you in invalidation. Here is the accounting.
What AI Coding Agents Still Get Wrong About Distributed Systems
Agents write correct-looking code very fast. The failures I keep seeing are not syntax or API misuse — they are assumptions about time, ordering and retries.