Ignore files in a git repo locally
I had a scratch file in a repo, some debugging notes I did not want to commit. Sometimes I added it to .gitignore, but I...
TIL — Today I Learned
Quick notes and discoveries from my learning journey
git rebase --autostash
Whenever I had to rebase on top of master with a dirty working directory (uncommitted changes), I always did the same four steps:
Rails picks the replica by request method, not by the query
We had this in ApplicationRecord and I was curious how it actually worked:
Migrating this blog from Tailwind v3 to v4
I moved this blog from Tailwind v3 to v4. The big change is that the configuration left tailwind.config.js and went into the CSS itself, with...
Idempotency keys stop duplicate charges
On a charge endpoint, a retry or a double click can turn one payment into two. The fix is an idempotency key. The caller sends...
Verifying an ECDSA signature in Go
We had a server-to-server callback that came signed, and I needed to verify it in Go. The flow is short: parse the public key (usually...
Postgres partial indexes for a WHERE you always use
We had a slow query. It filtered on a column where almost every row had the same value, and only a small part was the...
Go 1.21 added min, max, and clear
After I upgraded to Go 1.21, I deleted a few small helper functions. I had been copying them around for years.
find vs find_by to avoid noisy errors
Our error tracker was full of RecordNotFound exceptions. But these cases were fine. A missing row was expected, not a real problem.
context.WithTimeout won't stop a blocking call
I thought context.WithTimeout would cancel anything when the deadline passed. It does not. It only sends a signal. Your code has to watch the context,...
closure_tree: filter early
In a side project I use the closure_tree gem for hierarchical data in Rails. Methods like #leaves and #hash_tree are useful, but after I added...
Set max idle connections, not just max open
Under load we kept getting “bad connection” errors that came and went. The connection pool had a good max open setting, so that was not...
Events that must stay ordered go in the same Kafka topic
Kafka only guarantees order inside a single partition. Not across partitions, and for sure not across topics.
A good circuit-breaker fallback is the last cached response
When a circuit breaker opens because a downstream is failing, you stop calling it for a while so it can recover. The question is what...
Quorum is ceil(N/2)
Quorum is the smallest number of nodes that have to agree before a decision counts. The formula is ceil(N/2):
Rewrite the commit author across history
I committed a lot of work with the wrong author name, and some with a personal email that I did not want to make public....
Delete all evicted pods in one line
Evicted pods pile up and make kubectl get pods messy. They are done, but they just stay there. Here is a one-liner to clean them...
Every net/http request runs in its own goroutine
In Go’s net/http, the server starts a new goroutine for each incoming request. So your handlers run at the same time by default, even if...
Killing an N+1 with preload
A hot read endpoint was slow, and I could not see why from the code. The query log showed me the problem: one query to...
Pipe a .sql dump into a Postgres container
I needed to load a SQL dump into Postgres that runs under docker compose. The simple pipe:
Why bundle exec actually matters
I spent too much time on a build that worked for me but broke for a teammate. Same repo, but different output.