Posts on XKV.org

A Credit Limit Dropped From 100 to 50 and XKV Shows the Three Steps Behind It

Mon, 19 Oct 2026 00:00:00 +0000

A customer calls support. Their credit limit was 100 yesterday and it’s 50 today, and nobody told them why. The support agent can see the 50. Everything else is spread across three services.

The limits service set the 50, under its risk policy. The risk model raised the account’s score the day before. Billing had recorded a chargeback from the bank that morning. Each service did one reasonable thing, and each logged it in its own way. Putting the story together means knowing which logs to open and in what order.

A Q4 Price List Goes Out as One Transaction With One Reason

Mon, 19 Oct 2026 00:00:00 +0000

Prices change together. A new quarter’s price list touches every plan at once, and a half-applied list is worse than an old one: for a few minutes Pro might cost less than Basic. The list also has one reason behind it, usually a decision made in a meeting, with a ticket that tracked the rollout.

XKV writes the whole list in one transaction. Every price commits or none does, and every price carries the same reason, ticket and cause, given once.

A Timeout Raised During an Incident Explains Itself Three Weeks Later

Mon, 19 Oct 2026 00:00:00 +0000

At two in the morning an alert fires: the orders database is answering slowly, and order requests are timing out. The on-call engineer raises the database timeout from 5 seconds to 30 so requests stop failing while a replica catches up. It works. The alert resolves. Everyone goes back to bed.

Three weeks later someone notices the timeout is 30 seconds and wonders whether that’s a typo. Changing it back might be right. It might also bring the incident back. The person who knows is on holiday, and the incident channel has scrolled far out of sight.

An AI Agent Changed a Cache Setting and XKV Kept the Tool Call Behind It

Mon, 19 Oct 2026 00:00:00 +0000

An operations agent watches the product catalog. Its metrics show 4.1% of reads returning stale data, above the 2% target, so it shortens the catalog cache’s time-to-live from 300 seconds to 30. That’s a reasonable move. An hour later the catalog database is at 91% CPU, because the cache now sends ten times as many reads its way. An engineer puts the TTL back.

The next morning the team wants to know what happened. The questions are the usual ones, with a new twist: which change did the agent make, what was it looking at, and which of its tool calls did it? Agents act fast and often, so their changes need a trail at least as good as a person’s.

How XKV Was Tested With 1000 Kills, Torn Writes and a Million Revisions

Mon, 19 Oct 2026 00:00:00 +0000

A store that keeps the reason behind every value is only useful if it keeps the value too. So before 0.1.0 went out, each promise XKV makes got a test aimed straight at it, and every number below sits in the repository’s test results, written by one script on a 2-CPU Linux machine.

The promises are short. A transaction is all or nothing. An acknowledged write survives a crash. Committed data is never dropped quietly. Compaction never breaks a chain of causes. Here is how each was tried.

What an Explainable Key-Value Store Is and Why Small Values Need One

Mon, 19 Oct 2026 00:00:00 +0000

The values that cause the most trouble are small. A credit limit. A timeout. A price. A flag that switches a feature on for ten percent of users. Each one fits in a few bytes, and each one can stop a business for an afternoon when it changes and nobody knows why.

Every key-value store keeps the value. Some keep old values too. What none of them keep is the reason, and above all the link from one change to the change that caused it. That link is what people ask about. Support can already see the customer’s limit. What they need is why it’s 50 when it was 100 yesterday.

Why the Project Is Called XKV

Mon, 19 Oct 2026 00:00:00 +0000

XKV stands for explainable key-value. KV is the usual shorthand for a key-value store, the simplest kind of database there is: you put a value under a key and get it back later. The X is the part this project adds.

An X marks the spot on a map, and it’s the letter that stands for an unknown in algebra. Both fit. Every value in a store has a story behind it, and in most stores that story is the unknown. XKV keeps it next to the value, so the question every value should be able to answer, why, has an answer.

XKV 0.1.0 Is Released as an Open Source Key-Value Store That Remembers Why

Mon, 19 Oct 2026 00:00:00 +0000

XKV 0.1.0 is out. It’s a small key-value store for Go that keeps one thing other stores throw away: the reason. Every write records who made it, why, and which earlier change caused it. Ask a value how it got there and XKV walks the chain back, across keys, to where it started.

The release has four parts. The Go package, with no dependencies, stores everything in one file. The xkv command reads and writes that file from a shell and can serve it over HTTP for other languages. A WebAssembly build runs the same code in a browser, and the live demo is built on it. Four example programs act out the case studies on this site.