Yes, flatbuffers are fantastic. Let me know if you have any specific questions; happy to respond.
1. Are they easier to use than JSON?
2. Is it just putting strings into a big array?
3. Do you have an examples of them being used?
We were using protobufs at Spotify and ditched them for simple JSON calls on the client side. No one complained, and never going back to having anything like that on the client side if I can.
Just too many drawbacks.
For server to server, they might be fine, but to client just stick with JSON. (which when compressed is pretty efficient).
One could combine JSON and a serializationless library, your JSON would be blown up with whitespace, but read and update could be O(1), serialization would be a memcpy, you could probably canonicalize the json during the memcpy using the SIMD techniques of Lemire.
I did this one for reading json on the fast path, the sending system laid out the arrays in a periodic pattern in memory that enabled parseless retrieval of individual values.