Blog · page 5
Notes on engineering, design, and everything in between.
The N+1 query: the most typical ORM performance trap
Fetch 100 rows and query the relation for each one and you have made 101 queries. There are only three fixes: eager load, batch fetch, or use a single join.
Rate limiting: what token bucket and leaky bucket really differ on
A token bucket permits bursts; a leaky bucket flattens traffic to a constant rate. Picking wrong shows up as throttled normal users, or a limit that does nothing.
Catastrophic backtracking: why a regex can pin a CPU
Nested quantifiers make the number of match attempts grow exponentially; (a+)+b can hang a process on one long non-matching input. Drop the nesting or put a timeout on it.
iframe sandbox: it narrows capability, it does not harden
The sandbox attribute starts by removing everything and allow-* adds pieces back. Getting the direction backwards is common: scripts stop running because that is the default.
Semantic versioning: a major bump promises no silent behavior change
MAJOR does not mean big. It means breaking. Using it for refactors and hiding breaks in minor releases turns your downstream automatic upgrades into outages.
SQLite indexes: the leftmost prefix is a consequence of sorting
A composite index (a, b) can only order by b within equal a, so skipping a and filtering on b has nothing to use. See it as sorting and the mnemonic stops being a rule to memorize.