SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b370303b9617549e09a441b33b26eee1a17fe63f0384eface7aed79c21c76ea2' 
  AND token = '8bBvHniCuA3b+MyDlVtg86lwOC5zoxR38aWWuDWRBpU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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