See Mison paper at: https://www.microsoft.com/en-us/research/wp-content/uploads/2017/05/mison-vldb17.pdf
It follows exactly the design described in the Mison paper. Because there is no way to use avx2 extensions from the JVM this part is written in rust and wrapped in a native call. Also the predictive parsing part is not implemented, but because of the cost of building the Mison indexes I don't think it will change anything to the benchmark for small Json documents.
Benchmark (entry) Mode Cnt Score Error Units
Benchmarks.fastJson empty avgt 200 244.944 ± 25.159 ns/op
Benchmarks.fastJson short avgt 200 1171.627 ± 51.561 ns/op
Benchmarks.fastJson medium avgt 200 2967.922 ± 156.079 ns/op
Benchmarks.fastJson long avgt 200 12229.239 ± 407.896 ns/op
Benchmarks.fastJson huge avgt 200 118164.704 ± 3499.133 ns/op
Benchmarks.fastJson giant avgt 200 438202.179 ± 19309.856 ns/op
Benchmarks.jackson empty avgt 200 4872.127 ± 2271.468 ns/op
Benchmarks.jackson short avgt 200 9131.281 ± 7338.789 ns/op
Benchmarks.jackson medium avgt 200 5470.434 ± 534.308 ns/op
Benchmarks.jackson long avgt 200 11512.887 ± 889.058 ns/op
Benchmarks.jackson huge avgt 200 569606.131 ± 997983.165 ns/op
Benchmarks.jackson giant avgt 200 517020.023 ± 742322.271 ns/op
Benchmarks.mison empty avgt 200 2033.237 ± 85.180 ns/op
Benchmarks.mison short avgt 200 3312.618 ± 141.704 ns/op
Benchmarks.mison medium avgt 200 5707.338 ± 264.357 ns/op
Benchmarks.mison long avgt 200 8287.681 ± 562.832 ns/op
Benchmarks.mison huge avgt 200 38999.464 ± 3946.958 ns/op
Benchmarks.mison giant avgt 200 137388.974 ± 13729.804 ns/op
This mison implementation starts being more performant at the long test case (around 1kb). The overhead of the native call makes it less interesting for small json.
Perhaps it is possible to reduce this overhead (for example by using offheap memory directly from JVM code, and then just sharing a raw pointer with the native code). But for now I'm not convinced that for the common use case it will be possible to do something better as something like FastJson on the JVM.