analytically

  At 500 stations:
  - H3: 218µs, 4.7KB, 109 allocs
  - Fallback: 166µs, 1KB, 37 allocs
  - Fallback is 31% faster

  At 1000 stations:
  - H3: 352µs, 4.7KB, 109 allocs
  - Fallback: 312µs, 1KB, 37 allocs
  - Fallback is 13% faster

  At 2000 stations:
  - H3: 664µs, 4.7KB, 109 allocs
  - Fallback: 613µs, 1KB, 37 allocs
  - Fallback is 8% faster

  At 4500 stations (real-world scale):
  - H3: 1.40ms, 4.7KB, 109 allocs
  - Fallback: 1.34ms, 1KB, 37 allocs
  - Fallback is 4% faster

  Conclusion: The gap narrows as station count increases. At 4500 stations they're nearly equivalent. H3 has fixed overhead (~4.7KB/109 allocs for k=2 ring), while fallback scales linearly. The crossover point where H3 wins is likely
  around 10-20K entries.