Yes, Sesame has onboard memory saving history logs.
However, If you are the owner, Sesame doesn't save your logs in the onboard memory. All of your logs will be directly sent to Amazon's secure database by your phone. And only you can access this logs.
On the contrary, Sesame saves your guests' logs in the onboard memory and guests' phone are NOT allowed to send any logs to Amazon's secure database, since their phones might be jailbreak-ed or edited to send no/fake logs. We designed the product from the standpoint of Sesame's owners but not for the random users.
Once the owner(you) come home, your phone will fetch the guests' logs from Sesame's onboard memory(via Bluetooth) and upload them to Amazon's secure database. After that, Sesame will clear the onboard memory.
If you have Wi-Fi Access Point, Wi-Fi Access Point will upload the logs from Sesame's onboard memory(via Bluetooth) to amazon every second. So you can see guests' logs in real time and fetch those logs from anywhere.
Hope this help.