SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b43a03a0da8ae38382d20ce005ea1a795ec2f254715ee481cdfc4d290efee0d3' 
  AND token = 'kwChLdXx4fuxgwNn35NAMd5LkYmWLDFtLW++BY9XAzM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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