Short notes on latency, links and small self-hosted systems.
2026-10-18
Scheduling across time zones looks like simple arithmetic until a region changes its rules or daylight saving starts on different dates in different places. Storing a meeting as a moment in UTC loses the intent if the organiser's local rules change.
Calendars therefore store the local time plus the zone name. It is more complicated, and it is the only representation that survives rule changes.
2026-10-17
The maximum transmission unit is the largest packet a link will carry in one piece. When something along the path has a smaller limit and the signal that would tell the sender gets lost, large packets disappear while small ones get through.
The symptom is memorable: connections open fine, small pages load, and anything big hangs forever. Once you have seen it, you recognise it within a minute; the first time, it can eat an afternoon.
2026-10-16
Traceroute shows each hop on the way to a destination and how long it took to answer. The tempting mistake is to blame the first hop that shows a high number.
Routers often answer these probes slowly on purpose, because replying is low priority work. A hop with high latency matters only if every hop after it is also slow. Otherwise it is just a busy router being honest about its priorities.
2026-07-14
Average throughput is the number everyone quotes and almost nobody experiences. What a person notices sitting in front of a screen is the tail: the ninety-ninth percentile of round-trip time, the stall while a buffer drains, the half second before the first byte. A link can be fast and still feel broken.
2026-05-02
A two-gigabyte virtual machine is enough to run more than people expect, provided the parts are boring. One process per job, plain files for configuration, logs that a human can read without a query language. Complexity is rented, not owned.
2026-03-21
Anything written for an audience of one gets sloppy. Publishing forces the second pass where the actual reasoning shows up — usually along with the mistake.