[squarecog]

(ex-twitter engineer) I left before this project got started, and do not have any insider info on how they did it. Given what I know about the number of places tweet length assumptions were built into, it must have been a large, cross-team effort. It likely required thoughtful problem-solving.

Take, for example, search. An early iteration of Twitter search relied on this limit to pack term positions into 8 bits (Source: https://www.umiacs.umd.edu/~jimmylin/publications/Busch_etal...). 280 > 256, so if this was still around, the whole approach had to be rebuilt, and the indexes recreated. That's ... non-trivial. And that's just one subsystem.

[roymurdock]

Even more of a reason not to make this large, system breaking change.

[okr]

And i can imagine, when they just doubled the amount of possible characters, they just correlate these tweet buckets now. Like, maybe each tweet already had space for attributes/opcodes, so one can express things like "deleted". Maybe there is another attribute now: "has successors". And in the API one just return many tweets as one. In that way, one does not have to rewrite history. But who knows!

[akkartik]

Wow, sounds like Y2K.

[Xorlev]

At the volume Twitter works at, you take the constraints you can find.