SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ff42390ffb66c53287b91447df28da7c467bf488819a231061b2af9aa382e1ab' 
  AND token = 'jyU++ADBblMULdorTgnKoL9f90qeyFVl6fJg8aYvODs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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