SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'bdc6e2f58b5d98afd3c40613448fd2f8e4b1599d3104e3c23da20c4c954d53d3' 
  AND token = 'BCTVJVDwvn7dZcmEu8ShpF8WSO9oK+OGZj8KZ539Pgg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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