SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ad791406cf646bbfc62a40ecbb55eee7ec399fefd338912fa3352e28a721c76' 
  AND token = 'pFul00ay/wTcGZ+Vo2Mk9CTe53IkNLhcfcbvYSEfsEs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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