P99 0 ms* autocomplete for 240M domain names

This autocomplete suggests domains that don't exist. You can just type garbage and it will suggest something, but then if you go there, there are no records.

It seems like one purpose of an autocomplete box is help you avoid typos, so that makes it less useful.

Why not just trigger the fetch on keyDown and show it as soon as the response arrives, as usual?

The time it takes to press a key is a reasonable target to aim at for API latency I suppose, but it is still an arbitrary target. Waiting to display until keyUp just adds more latency if your API is faster. Having it synced with keyUp doesn't make it feel more immediate to me.

Using keyup makes no sense and is inconsistent with user expectations. For triggering actions (which includes normal typing), you only ever use keydown. (Well, there’s one exception for reasons unclear to me: activating a button by pressing Space. That triggers on keyup like how clicks are on release, while Enter triggers on keydown.) Keyup is limited to things where you’re constantly reacting to the state of a key, as is common in games.

This affects the functionality, too. It is in fact introducing latency by using keyup instead of keydown. Feels bad.

Unfortunately this approach doesn't feel that great down here in Australia, definitely a function of latency.

I think you could get a lot closer by framing this as an optimization problem, where you use the full alphabet dictionary, but add a residual prediction which aims to cover as much of the remaining domain name tree as possible weighted by popularity. This tree could then be pre-baked and stored with the same system. This would probably get you p99 0ms even in Australia.

If you’d like to reduce the network latency further you can store each trie node as a file, naming it conveniently the prefix path to that node. Then dump the few hundred million files onto R2.

Now the traversal can be done completely via CDN lookups!

Clever but that’s not how we measure latency.

Looks more like 500ms?

KeyDown events don’t work great for mobile, though.

Autocomplete aside, this is a pretty nifty tool.

Pretty sure we mean < 1ms rather than actually instantaneous.

its pretty clever but what happns when someone pastes a domain or uses IME or voice input? the api being that fast is still impressive.

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