Customers mostly want high performance and high security for their programs. What strategies do you use to achieve this?
First, you cannot make any assumptions on what they want (like high performance or security). You need to determine what they want and what the purpose is. Often, the want and purpose will be different!
Usually, you need to have the client backup and start the story from the beginning. What issue are they trying to solve? Do they need a custom solution for it? What is the benefit from the solution and is it worth the cost?
Then you work with the client to develop the balance of all the aspects...such as performance vs cost, security vs usability/cost, performance vs. quality, etc. Find out what aspects are most important to them and work to optimize that. And never let them say "everything" unless they have an unlimited budget ;)