SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '35881745ef016e759d73118c6ec43fef1b892f863048d629c80acaea5181653e' 
  AND token = '53R5fLMbzI7Sq+PiTG+dFGvhMqeOPBs+ZeHLEQrKpMU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}