SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8b5d1501a3ddffa381a7536a722b09ae4514b71fd25efb66c421ddfc6520e093' 
  AND token = 'q/zVIlO/j/7LLTZE1ATcyELQgz/a8wuJ2nHfGmQxKvY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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