SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c21b7a4333cba589419e11bd78e2ab2d1c855ec5d95d1c4f07d5431d62dd9526' 
  AND token = 'fcd10b8SUMkP8A20I6+MN48b9eJZRqduZk5LPir2XUo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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