Notes from a developer who likes to dig until things make sense.https://dighard.dev/https://dighard.dev/posts/tornado-postgres-connections/https://dighard.dev/posts/tornado-postgres-connections/Our Tornado app hit PostgreSQL's connection limit. When I looked closer, most of those connections were just sitting there, idle or stuck in a transaction.Wed, 28 Oct 2026 00:00:00 GMTpostgresqlpythontornadoincidenthttps://dighard.dev/posts/runbooks-and-playbooks/https://dighard.dev/posts/runbooks-and-playbooks/A runbook tells you how to do a known task. A playbook tells you how to think when you don't know what's wrong yet. I needed both.Tue, 20 Oct 2026 00:00:00 GMToperationsincidentdatadogpostgresqlhttps://dighard.dev/posts/postgresql-vacuum/https://dighard.dev/posts/postgresql-vacuum/If PostgreSQL never overwrites a row, where do all the old versions go? And why didn't my table shrink after I deleted most of it?Thu, 24 Sep 2026 00:00:00 GMTpostgresqldatabasesoperationshttps://dighard.dev/posts/postgresql-mvcc/https://dighard.dev/posts/postgresql-mvcc/What does transaction B see while transaction A is changing the same row? I finally sat down to find out what happens under a simple UPDATE.Thu, 10 Sep 2026 00:00:00 GMTpostgresqldatabasesinternalshttps://dighard.dev/posts/zero-downtime-deploys/https://dighard.dev/posts/zero-downtime-deploys/Our system takes payments all day, so every deploy meant downtime. Here's how we got to rolling deploys without Kubernetes, one question at a time.Sun, 02 Aug 2026 00:00:00 GMTdeploymenttraefikdockerpostgresqlhttps://dighard.dev/posts/ufw-docker/https://dighard.dev/posts/ufw-docker/I denied a port in UFW, but the container behind it was still reachable from the internet. It took me a while to stop blaming UFW and start reading iptables.Tue, 21 Jul 2026 00:00:00 GMTlinuxdockernetworkingsecurityhttps://dighard.dev/posts/restore-your-backups/https://dighard.dev/posts/restore-your-backups/We had nightly backups that nobody had ever restored. Then someone asked what we'd get back if we lost the database at 2 PM.Sun, 14 Jun 2026 00:00:00 GMTpostgresqlbackupdisaster-recoveryhttps://dighard.dev/posts/hazelcast-kubernetes-discovery/https://dighard.dev/posts/hazelcast-kubernetes-discovery/Scale a Hazelcast deployment up and the new pods just join the cluster, with no member list anywhere. I liked that it worked. I didn't like not knowing why.Fri, 05 Jun 2026 00:00:00 GMTkubernetesdistributed-systemsjavahazelcasthttps://dighard.dev/posts/spring-reactive/https://dighard.dev/posts/spring-reactive/I could read Mono and Flux, but I couldn't say what they actually bought anyone. So I sat down and figured out what "reactive" really changes.Mon, 04 May 2026 00:00:00 GMTjavaspringconcurrencyhttps://dighard.dev/posts/docker-networking/https://dighard.dev/posts/docker-networking/How does a container reach another container, the host, or the internet underneath? What actually carries the packets?Wed, 22 Apr 2026 00:00:00 GMTdockerlinuxnetworkinghttps://dighard.dev/posts/spring-modulith/https://dighard.dev/posts/spring-modulith/Our customers couldn't run a dozen microservices, but our monolith was getting tangled. Spring Modulith gave us boundaries without the containers.Fri, 20 Mar 2026 00:00:00 GMTjavaspringarchitecturehttps://dighard.dev/posts/isolation-levels/https://dighard.dev/posts/isolation-levels/Just querying the database as usual works, right up until two people try to book the last ticket at the same time.Tue, 22 Jul 2025 00:00:00 GMTpostgresqldatabasestransactionshttps://dighard.dev/posts/how-tls-works/https://dighard.dev/posts/how-tls-works/I thought I understood the TLS handshake. Then I dug a little deeper and found out the picture in my head was from an older version of TLS.Fri, 14 Mar 2025 00:00:00 GMTsecuritynetworkingtlshttps://dighard.dev/posts/dependency-injection-over-hardwiring/https://dighard.dev/posts/dependency-injection-over-hardwiring/A static utility class looked tidy, until I tried to test it. Notes on Effective Java's Item 5, and why it stuck with me.Mon, 18 Nov 2024 00:00:00 GMTjavadesigntestinghttps://dighard.dev/posts/java-reflection-change-annotation/https://dighard.dev/posts/java-reflection-change-annotation/Annotations are supposed to be fixed once the code is compiled. I needed one to change, so I went looking for where Java actually keeps them.Tue, 08 Oct 2024 00:00:00 GMTjavareflectiontesting