SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '475ada794cedbb06f5bd13e9c1f8cd5c84b9a96518915930830b3f88caa6e688' 
  AND token = 'rkDhtvvEBYdAe81Feh/4qKuBQJrF1WPO7NW+4PiiVHQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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