SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '46f4781660fee177b13875a1e408f0cc9ae0d725630de4fd98e504858746a94b' 
  AND token = 'zlMZPRKh+XyOV2pp1ScBbwoDXJ4gYHusgacxe3QpK68=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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