The serialization format here was designed so you can parse it (or detect a parse error and bail out) in a single O(n) pass through the message data. No backtra

The serialization format here was designed so you can parse it (or detect a parse error and bail out) in a single O(n) pass through the message data. No backtracking required. (You mentioned strings, so I'll use that to give flavor: a string is represented as a one-byte prefix, followed by a byte length, followed by that many bytes of UTF-8. I'm not sure whether you'd categorize this as fixed or variable length, but that's how it's represented on the wire.)