[jholman]

First of all, I believe that Kenton Varda is not the inventor of protobuffs, but rather a Google engineer who did a bunch of work on Protobuffs v2 (I believe on both of the v2 specs for protobuffs, because there are two different v2s). He is certainly quite knowledgeable, but not "the inventor".

Second, while he does characterize it as a "huge mistake" for encoding/decoding performance reasons, there are a few caveats that are obvious here.

1) Half of his remarks here explain why varints are inappropriate for CapnProto, a separate project of his, inspired by his experience with protobuffs. CP has different design goals than PB, and in that context varints are inappropriate. Fine.

2) His argument here against varints in protobuffs (as contrasted with in capnproto) is only that they cost CPU time (and thus latency). That's surely true, but it's not at all clear to me that he's right that this is, in general, the wrong performance tradeoff.

3) In general, if you want to represent a long-tailed distribution of numbers, some variable-length encoding has merits, because the alternative (that protobuffs promote, IIUC) are fixed-width ints, which means you waste a lot of space to accommodate your long tail, and even so you might not have allocated enough space for the largest integer you ever need to handle.

[kentonv]

FWIW, before I even joined Google, there were notes from Sanjay (the actual inventor) saying that varint was a poorly-chosen format due to excessive branching. IIRC he was arguing for a format where you can tell the length based on the first byte although I don't completely remember. In theory you could design such a format that is just as space-efficient as varint, by re-arranging bits.

Protobuf -- like most successful systems -- was not so much "designed" as it was "evolved" as a series of decisions made out of expediency rather than because they were the best possible answer. Overall it has obviously worked extremely well, but I would not assume that just because protobuf does something, it is good. (But I'd say that about just about everything, not just protobuf.)