The ruby version looked a bit odd to me. It would be unusual to not use regex in this context. I'm not sure if this is in the spirit of the test, but using reg

The ruby version looked a bit odd to me. It would be unusual to not use regex in this context. I'm not sure if this is in the spirit of the test, but using regex reduced the time from 27s to 0.04s on my machine. require 'benchmark' contents = File.read("/tmp/200mb.txt") find = "07123E1F482356C415F684407A3B8723E10B2CBBC0B8FCD6282C49D37C9C1ABC" result = nil elapsed = Benchmark.realtime do result = (contents =~ /#{find}/) end puts "Found at index #{result} in #{elapsed}s" (The search string was placed at the end of a 200mb file)