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Comment by lj3 | Hacker News Reader

Do you have any opinions on Cap'n Proto vs Extprot[0]?

I hadn't heard of Extprot before so I took a quick look. It appears to be heavily inspired by Protobuf, having almost exactly the same arrangement on the wire, adding a few tweaks but keeping many idiosyncrasies.

The Cap'n Proto documentation compares it extensively with Protobuf and most of those comparisons probably apply to Extprot as well.

(Disclosure: I am the author of Cap'n Proto and also Protobuf v2.)

I haven't seen Extprot before you mentioned it. That said, it appears to require deserialization and that's something we avoid. LMDB can hand you back a pointer to your object in the memory map, and we can easily use that pointer with Cap'n Proto without any calls to malloc().

What are your thoughts on SBE vs Cap'n Proto. I don't know much about serialization libraries, but was thinking about looking into these both soon. Since you are using Aeron, I thought you would have looked into SBE( since developer being same for both) and not decided to go with it.

SBE is better if you don't have (much) in the way of message format evolution and you intend to read each message in full.

Cap'n Proto has a way better compatibility story, and there's no need to read the entire message just to read a particular part.

SBE is very good for its intended use case: high-frequency trading with tiny, but tons, of small messages. Cap'n Proto is better for use as a stable (but evolvable) message format between systems (e.g. RPCs), or for on-disk storage if you've got a database (like LMDB) that doesn't force you to copy read-only data.

Thank you! I'm very newbish on this stuff, but I'm trying to learn.

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