Grep is inefficient search engine, because it needs to scan through whole content (and Telegram uses search indexes). Also, grep cannot deal with words forms and inflections (you type "foot" and you also want to find "feet"). Inflections are not very important in English, but you need to deal with them in other languages where the word can have many forms.

I'm not trying to claim Telegram uses grep or whatever. My point is even very active chats on telegram generate somewhat small amount of text data and I dont believe that searching through it require massive complex search engine with super-fast backend.

I basically participate in hundreds of chats and message history doesn't take 10 of GBs. And I also know that search in history of such chats isn't so snappy on older Android phone.

Not at all. Try searching 500/1000 sources (maximum number of conversations any free/premium user can be part of), each with potentially millions of messages, and providing the results in under a second.

AFAIK telegram dont have any super-advanced search features neither it instantly return you results for all these years. Also if you search less common terms it's usually take longer than less than second.

And if you just run client on device without a lot of this history cached search wouldn't be anywhere as fast as you expect. So I pretty sure there no server-side magic there, but instead very good UX.

Also I can tell for certain that with right index grepping tons of JSONs can be very effective on any modern devices.

Can't say there aren't others who've used my search terms, but some things I search for are pretty unique. And I do a lot of searching. And search speed is consistently sub-second. There's no trickery seeing years-old results from VERY heavily used chats appear instantly. There's heavy optimization happening for search, and I'm very certain default e2ee would destroy that experience. Unless you can point to 1 e2ee service working at that scale with comparable UX. I won't even touch on the local aspect as the amount of storage needed to just store the data is waaaay beyond anything I'm even interested in owning, much less the compute to make it so accessible.

> Also I can tell for certain that with right index grepping tons of JSONs can be very effective on any modern devices.

But to run local search you need to download the conversations to device first which might require lot of (expensive) traffic.