parco VS jsoniter

Since most of the time would be spent decoding json, you could try to cut this time using https://github.com/bytedance/sonic or https://github.com/json-iterator/go, both are drop-in replacements for the stdlib, sonic is faster.

We all know the builtin golang JSON parser is slow.

How about doing comparisons against other implementations?

Like this one: https://github.com/json-iterator/go

Json-iterator (https://github.com/json-iterator/go), you can replace all of encoding/json with this. It does the same thing but it's faster.

Do you want to look at every field all at the same time? If not, you can pick out individual fields. There's other packages such as https://github.com/tidwall/gjson or https://github.com/json-iterator/go that let you pass in paths such as "a.b.c" to extract single fields.

For each Go type used within the config, we generate a separate unmarshaller function. The unmarshallers use json-iterator to process the output from CUE, while tracking the path within the config to the unmarshalled value. This path tracking will allow the function to check if live overrides have been provided on that path and return the override instead.

https://github.com/json-iterator/go an alternative JSON encoding package which allows to stream (flush out) encoded data as soon as it's able to (which is in contrast with the stock package which buffers everything until the encoding is known to be complete and OK).

What to use Easyjson is about the top of the pack and it's straightforward. The downside of efficient tools is that they use code generation to create the code required to turn your structs into json to minimise allocations. This is a manual build step which is annoying. Interestingly json-iterator also uses reflection but it's significantly faster. I suspect black magic.

jsoniter for low level access to JSON encode and decode

Takes like 10 minutes to write and parses very efficiently. https://github.com/json-iterator/go looks like it can provide such simple parsing