SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c4d6a874e76e09231cf8d10a3111df77a45526198b03946fa04f1fdb8277c5e5' 
  AND token = 'VztCB/6noxeEsCGp1AgYAhFWFgkZdWK85ABb+dV9uzE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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