Tag
5 posts
Build log
Every minute, every open order against every rider on duty, solved as one vehicle routing problem with VROOM. How the round works, why the solver's answer is only a proposal, and why the legs are diffed instead of rebuilt.
17 min read
Build log
at and cron as a service, in Go: six services, MySQL as the queue, Cassandra for history. The decisions behind it, their trade-offs, and what load-testing it on an AWS-shaped bench found, including a bug of mine.
onSystem Design postsDatabase Internals postsGo posts
11 min read · Part 1 of Building a distributed job scheduler
Build log
An EKS and RDS lookalike on one PC, a cron platform with 30,000 jobs due at 09:00:00, and ten tests. Nothing was lost; the 300 jobs/s ceiling turned out to be an N+1 of mine.
onSystem Design postsDatabase Internals postsGo posts
11 min read · Part 3 of Building a distributed job scheduler
Build log
Why the jobs table is the queue, why MySQL and not Postgres, why Cassandra only for history, and how leases, fencing tokens and idempotency keys keep at-least-once honest. With the alternatives I rejected and the SQL behind each decision.
onSystem Design postsDatabase Internals postsGo posts
12 min read · Part 2 of Building a distributed job scheduler
Deep dive
How database indexes work internally with B+ Trees, why transactions lock rows, and how both are deeply connected. Explained for backend engineers who want to stop guessing.
12 min read