In this final chapter, we have started learning the relevance of optimization and why we should avoid premature optimization by measuring. Then, we jumped into the topic of measuring by learning different mechanisms to measure the time of execution for our regular expressions. Later, we found out about the RegexBuddy tool that can help us to understand how the engine is doing its work and aiding us in pinpointing the performance problems.

Later on, we understood how to see the engine working behind the scenes. We learned some theory of the engine design and how it's easy to fall in a common pitfall—the catastrophic backtracking.

Finally, we reviewed different general recommendations to improve the performance of our regular expressions.