By not taking the full-range into account, I was not really getting the "max suffix", so when I was trying to insert a new entry with name "$prefix $max_suffix_int", I was again getting a conflict, which triggered another loop necessary for a different conflict resolution scheme (the new one is supposed to find a non-conflicting name in a single pass, at the cost of scanning the range of possible conflicts to find the max_suffix_int of really conflicting entries - some entries have the same name, butother keys make them non-conflicting).

I also tested that both lower_bound(prefix + " :") and upper_bound(prefix + " 9999999999") (I use an int32_t suffix) give me the same upper range iterator, with similar performance.