Another approach could be to use prefixes. A 0 could separate the prefix (fixed hash part) from the suffix (random part). 0<suffix> 10<suffix> 20<suffix>

Another approach could be to use prefixes. A 0 could separate the prefix (fixed hash part) from the suffix (random part). 0<suffix> 10<suffix> 20<suffix> ... Combined with auto-completion, you preserve the main advantage (ordering) and you are able to quickly compute the hash.