Field notes — essays & research notes

Things I've written down.

Ruby, Rails, performance, security and applied machine learning. Updated when something feels finished.

2 posts in Big Data
BIG DATA 05 / 22 / 26

One task running for an hour while 199 sit idle

Skew is the most common reason a Spark job is slow, and it looks exactly like a job that is nearly finished.

3 min
BIG DATA 11 / 03 / 25

One line of PySpark, 34% off the runtime

Broadcast joins, two million records, and why Spark's default query plan is worth arguing with when you know something the optimiser doesn't.

4 min