SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '473ca28c21fc59578c0c1d9a899e9f76036833ecd7b51f0863b1fa51b75df4e1' 
  AND token = '2kwlMtJ+gYv9oXAV+aSkTiLNCnXUZ2vAc1v6A2J83dM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}