SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3a08c38195bb20116f9a4232110d4bbd068468159e888c92ce6edc04117f771' 
  AND token = 'urKXcWs8JjVbWZ5rqnKQRv5mwH3D+84O6FgjHOPHXIU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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