How a web page grows old
HTTP caching is an agreement about when old information may stand in for another request. The interesting question is what each page can afford to mean by current.
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About the author
Ellis Vale
I write about the details that connect computing to ordinary life: what a saved record means, how a letter reaches a screen, and which assumptions travel with a file.
At Systems With Memory, I follow questions of time, text, trust, and long-term access through primary documentation and original research. I use concrete examples in my essays to make technical ideas easier to examine.
Stories by Ellis Vale
12 stories
The order of records in an append-only log
A log gives records an order within a defined stream. Partition keys, retries, consumer progress and retention decide what that order can actually promise.
Counting characters: four rulers for the same text
An accented letter and an emoji expose the choices hidden inside a character limit. A worked example separates bytes, code units, code points, and grapheme clusters.
What a backup restore actually proves
A restore test becomes useful when it names the data, dependencies and user actions it recovered. Integrity checks and a working application provide different evidence.
Checksums and the context an archive keeps
Bit integrity is essential to preservation. It becomes useful cultural memory only when an archive also preserves context, formats, and relationships.
The units that travel with a CSV file
Parsing a table is not the same as understanding it. A small weather-log example shows where types, missing values, and measurement meaning enter the exchange.
The hidden work between a letter and a pixel
Text on a screen is assembled through font selection, shaping, positioning, and rasterization. Following those stages makes typographic differences easier to understand.
What a reproducible build can testify to
Matching binaries are powerful evidence about a build. Understanding the claim means separating repeatability, provenance, and the quality of the source.
A merged document can still be wrong
Automatic convergence solves a precise problem. Collaborative software still has to make disagreement visible and leave room for judgment.
The paths that put events in order
Ordering log lines is easy. Explaining which event could influence another requires a more careful account of distributed time.
SQLite WAL: where committed pages live
A write-ahead log changes where committed work lives. That small fact explains concurrency, checkpoints, and why a casual file copy can mislead.
Following a packet through policy and measurement
BGP policy, round-trip timing, and traceroute each reveal a different network. Reading them together takes more care than drawing a shortest path.