The first bottleneck you should be considering is how your application scales vertically. Vertical scale typically has direct correlation with your applications performance characteristics. Vertical scale is achieved by increasing CPU, Memory, Network Capacity, or Disk your application has available to it. Is your application going to be CPU or Memory bound? Will you require a lot of Disk I/O? How much data will you be reading/writing over the network? You need to understand each of these areas in order to know how your application will scale vertically.
How your application scales horizontally is the next potential bottleneck you should understand. Horizontal scaling is the ability to add additional machines running your software into an existing pool to add additional computing. Horizontal scaling allows you to increasing the throughput of your application by having more capacity to process requests or jobs that the application performs. Your software needs to take this into account from the beginning or it won't last without requiring rework.
Another area to consider when understanding your applications bottlenecks is how stateful it is. Does your application require some external state in order to run? How the application gets and maintains this state can lead to potential bottlenecks. E.g maybe your application needs some specific information about the user making the request that it has to lookup somewhere. Or maybe it needs information about previous requests. An example of a stateful application is one that uses a shared database. The reason state cases bottlenecks is because your application is now dependent on something external that it does not control.