Original, source-backed articles about running small systems, static sites, HTTP, DNS, TLS, and operations.
Posts are original articles written for this site. Each one is script-free, source-backed, and tied to the same operational reality the rest of the site records: how a small, static, publicly served system is built, secured, and kept honest.
Redis Lua scripts run without interleaving
A Redis Lua script can read data, make a decision, and update it without another client’s command interleaving between those steps. It does not mean every statement succeeds, that earlier writes are undone after an error, or that the result is automatically durable.
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High-cardinality labels increase stored series before anyone queries them
A Prometheus series is identified by a metric name and its complete label set. Adding customer or request identity to a counter can create many series even when every dashboard immediately sums those identities away. Query aggregation changes the returned result; it does not remove the raw series that were ingested.
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A checkpoint flushes dirty buffers to disk
A checkpoint establishes a starting point for PostgreSQL crash recovery. It synchronizes the data-file changes required for that checkpoint and records the corresponding recovery information. WAL must reach durable storage before dependent data pages are written. This ordering allows committed work to survive without forcing every modified table page to disk at each commit, while recovery can replay later changes when necessary.
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nginx burst capacity decides which requests wait and which are rejected
nginx request limiting uses a leaky-bucket method to account for excess requests against a configured rate. The burst allowance determines how much excess can be accepted, while nodelay and delay affect when accepted excess proceeds. These are admission and scheduling decisions. They do not make every request above the nominal rate fail, nor do they measure concurrent application work.
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A Redis list and a sorted set solve different problems
A Redis list stores an ordered sequence that permits repeated values. A sorted set stores unique members ordered by numeric scores. The useful distinction is not that one is universally faster or cheaper: it is whether the application needs positional sequence operations, unique membership, score ranges, or a combination requiring a different data model.
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VACUUM FULL rebuilds a table instead of pruning it
After a large deletion, a PostgreSQL table may retain a large file even when only a small fraction of its rows remain. Ordinary vacuum makes obsolete space reusable; VACUUM FULL rewrites the surviving contents into a new file and rebuilds indexes. That stronger reclamation has a different lock and capacity budget, so it belongs to planned maintenance rather than routine reaction to a large size number.
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Shell word splitting turns unquoted variables into several arguments
A shell variable holds a string, but an unquoted expansion can turn that string into several command arguments. In Bash, word splitting examines expansion results using IFS as the delimiter set. This is why a pathname that works when typed with quotes can fail after being stored in a variable. Debug the arguments the receiving command actually gets, including empty ones, before blaming the filesystem.
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AAAA records publish IPv6 addresses without proving reachability
An AAAA resource record contains one 128-bit IPv6 address. An A record contains an IPv4 address. A name may have either type, both types, or several addresses within each type. These are separate RRsets, so A and AAAA can have different TTLs. Publishing AAAA makes an address discoverable through DNS; it does not create an interface, route, listener, or working application.
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