GenerateMatch.cs

static void GenerateMatch(string key, ref string prefix)
{
    var orig = GetShardId(key);
    var tries = 0;
    var sb = new StringBuilder(prefix).Append("-");
    while (true)
    {
        for (int i = 0; i < 25; i++)
        {
            tries++;
            sb.Length = prefix.Length + 1;
            sb.Append(Convert.ToBase64String(BitConverter.GetBytes(tries)).Trim('=').ToLower());
            if (GetShardId(sb.ToString()) == orig)
            {
                prefix = sb.ToString();
                return;
            }
        }
    }
}