Heuristic expressions are mathematical formulas that use specific rules of thumb which provide a quick solution to a problem. They are often used when an exact answer isn’t available or when there’s not enough data to make an accurate calculation. This allows the software architect to quickly come up with approximate solutions that may still be useful while avoiding spending too much time on complex calculations. Heuristics can be used in virtually any area of software engineering, but they have become especially popular in testing and debugging. When developers are trying to debug a program, they may not have time or resources to carefully trace every line of code and identify the source of errors — instead, they might use heuristics to quickly pinpoint potential sources of errors. For example, if they notice that certain pieces of code seem to cause more errors than others, then they can apply heuristics such as “code X is likely causing Y error” or “code X is likely related to Y issue”. This helps them narrow down the number of lines of code that need further investigation and save precious time in the process. Heuristics can also be used by architects when designing architectures for their applications. By using heuristics such as "this component will likely have high traffic" or "this component will likely require more storage", architects can quickly determine which components should get priority during design and implementation phases, saving them time and energy while still ensuring that their application performs optimally.