vespa-engine/vespa: technical due diligence, read from its repository

The median source file here is 63 lines. 41 files exceed 1,000 lines, the largest being 2,787. Size is not a defect on its own — some problems genuinely live in one place — but these are where merge conflicts, review fatigue and single-owner knowledge concentrate, and they are the first thing that slows an inheriting engineer down.

56 files were marked deprecated over two years ago and still are, the oldest since Jun 2021. A deprecation is a promise to remove. Ask what still depends on these, and whether removing them is scheduled.

Strings shaped like credentials appear only where fakes are usual: test fixtures, examples, documentation, placeholders and local stacks. They are almost always fakes. Ask someone to confirm that none of them works anywhere, because a real key in a development file is still a real key.

3 HTTP calls use a client with no timeout (Python `requests` without `timeout=`, or Go's default client). When a dependency slows down, each one holds a worker until the connection gives up, and enough of them take the service down with the dependency.

1 places in product code build SQL by formatting or joining strings rather than passing parameters. 1 of them put a value into the string; in the rest, what the code shows going in is a table or column name, a constant, or something the line does not show. Ask whether any value reaches these strings, rather than a parameter.

3 of 526 locked dependencies match 10 published advisories in OSV, 3 of them rated high or critical. A lockfile says which version is installed, not whether the flawed code is reachable from this product, so each needs a look. Most are fixed by an upgrade, and the advisory names the version. This lockfile pins development tools alongside what ships and does not say which is which, so some of these may never reach a user.

Nothing in the service initialises an error reporter (Sentry, Rollbar, Bugsnag, Honeybadger or an APM agent). An exception in production reaches a person only if someone is reading the logs, which usually means a customer reports it first.