PowerApps is a no/low code application development platform. Apart from facilitating faster application development, it allows non-professional developers to develop software.
As it is a hosted & shared platform, it comes with some platform protections in form of limits and throttling to ensure a bad piece of software does not bring the platform down. Also it brings in some new best practices to ensure that software developed in performant.
Here is a guide which collects detailed guidance around building scalable and performant PowerApps. It covers content available throughout the app lifecycle.
We want to build an app for 50K — 500K users with 500–5K concurrent users. Is this possible? If yes, which data sources can I use?
What are the limits (tenant / environment / app / user) we need to keep in mind while evaluating the app for each data source / connector?
What are the design best practices we should follow for such large-scale apps?
What are the common performance Issues and how can we address them while we design/develop?
What tools are available at development stage to develop for scale and development?
Once we have built app, how can we load test it to ensure that it scales and performs as expected?
Once in production, how do we proactively monitor performance?
When facing performance issues, how can we troubleshoot and resolve?
You can access the guide here. I will be updating it frequently so do revisit for latest updates.