SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '956831f3493288d416d21f7f0da835eccbaff7cf421038bdfde7f1397a3040e8' 
  AND token = 'S+/8gSu4HEhCupOOs+JAUc9IB4AN9pnZExJDB+kYOUQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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