We are aware that some users are experiencing performance issues while running Shift. Shift was built on a framework called Electron which uses an integrated Chromium build. Chromium is the open source project which powers Chrome. Essentially, when you run Shift, you are running another copy of Chrome in the background. If your computer memory is constrained, running Chrome, Shift, or any other memory intensive applications can potentially slow down your computer. We are continuing to improve Shift to minimize these possible slow downs to your system.
Goods news is that we recently came out with a feature that alleviates this problem. Our newest hibernate feature allows users to snooze their accounts in order to recover lost memory and processing power associated with running multiple tabs. But don't worry, all email and calendar updates will continue to populate as before from both your active and hibernating accounts.