SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fc3763e1f69f94ac4686adb6953216a1280fe70a629058df2cef11679d14642a' 
  AND token = 'c4uEcXmKviEgzzKlL/75pE8OtDUULEumLKFgkHwFLZg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00051

JSON explain

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