SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7c39fe6ed7c697c101163c8c74849169cce5f4518f41e62b251a1b476ae9e3b3' 
  AND token = 'lFfYbEwxWEgKG3GWRNvYRUEYskaSydktoYNIVuECZ/s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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