SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21fd6ecb8a065dec2438a0f4957c744b1702d4cb5c4b513abf341e8a17a245b4' 
  AND token = 'yTzQv7Q+lVaWJ4W8VG8BzuSDLnOByueTYebZ9vs4JGw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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