Thanks for the pointer, I had only checked the 'main' branch, which doesn't have the benchmarking code present.

When running on the commit & code you point to here, here are my new results:

  $ hyperfine -N --warmup 5 './benchmark/fast_parser data/fastq_test.fastq'  './benchmark/needletail_benchmark/target/release/rust_parser data/fastq_test.fastq '
  Benchmark 1: ./benchmark/fast_parser data/fastq_test.fastq
    Time (mean ± σ):     675.0 ms ±   2.4 ms    [User: 399.3 ms, System: 269.4 ms]
    Range (min … max):   670.5 ms … 677.5 ms    10 runs
  
  Benchmark 2: ./benchmark/needletail_benchmark/target/release/rust_parser data/fastq_test.fastq
    Time (mean ± σ):     840.8 ms ±   3.0 ms    [User: 578.0 ms, System: 257.0 ms]
    Range (min … max):   837.0 ms … 847.7 ms    10 runs
  
  Summary
    ./benchmark/fast_parser data/fastq_test.fastq ran
      1.25 ± 0.01 times faster than ./benchmark/needletail_benchmark/target/release/rust_parser data/fastq_test.fastq

Which indeed shows your parser running about 25% faster than the needletail version.