https://www.youtube.com/watch?v=OsyKxWxGtiI

Your API returns a user. Three fields — an ID, a name, a bit for active. That exact payload, as compact JSON, is forty-one bytes on the wire. As protobuf, it's twelve. But compactness is the least interesting thing about protobuf. The real reason Google built it is something JSON fundamentally cannot do.

The JSON bill you pay on every request

Take this payload:

{ "id" : 12345 , "name" : "Alice" , "active" : true }

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Twelve bytes of that are actual data. The other twenty-nine are JSON describing itself — quotes, colons, commas, and the key names id , name , and active spelled out in every single message. Every request. Every response. Forever.

You can compress it. You can minify it. It still has to spell itself out on the wire because every reader has to parse a self-describing document.

The real problem isn't bytes — it's fragility

A week later you add a field: email . You ship the new server.…