local key         = KEYS[1]           -- identifier including prefixes
  local maxTokens   = tonumber(ARGV[1]) -- maximum number of tokens
  local interval    = tonumber(ARGV[2]) -- size of the window in milliseconds
  local refillRate  = tonumber(ARGV[3]) -- how many tokens are refilled after each interval
  local now         = tonumber(ARGV[4]) -- current timestamp in milliseconds
  local incrementBy = tonumber(ARGV[5]) -- how many tokens to consume, default is 1
        
  local bucket = redis.call("HMGET", key, "refilledAt", "tokens")
        
  local refilledAt
  local tokens

  if bucket[1] == false then
    refilledAt = now
    tokens = maxTokens
  else
    refilledAt = tonumber(bucket[1])
    tokens = tonumber(bucket[2])
  end
        
  if now >= refilledAt + interval then
    local numRefills = math.floor((now - refilledAt) / interval)
    tokens = math.min(maxTokens, tokens + numRefills * refillRate)

    refilledAt = refilledAt + numRefills * interval
  end

  if tokens == 0 then
    return {-1, refilledAt + interval}
  end

  local remaining = tokens - incrementBy
  local expireAt = math.ceil(((maxTokens - remaining) / refillRate)) * interval
        
  redis.call("HSET", key, "refilledAt", refilledAt, "tokens", remaining)
  redis.call("PEXPIRE", key, expireAt)
  return {remaining, refilledAt + interval}