SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f8b4fc243b829a3b34d976a3ccefb773a4b2f49302ae134076e8db427a97a792' 
  AND token = 'fub+pygIYyAqCz1KTHvOiXV65dlQBv7CN/mWXLlApt8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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