In the closing keynote of RailsConf 2018, Aaron Patterson presents a light-hearted yet insightful talk focusing on performance in Ruby on Rails applications. He humorously reveals his procrastination and shares anecdotes to engage the audience while seamlessly transitioning into the core topic: optimizing development speed over time.

Key points discussed include:
- Procrastination and Humor: Aaron begins by joking about his procrastination habits, using humorous coding puns related to Git. This sets a relaxed tone for the presentation.
- Become Better Developers: He encourages developers to focus on improving their unique business logic rather than relying solely on generic features offered by frameworks.
- Declining Team Velocity: Aaron highlights the paradox where, despite learning new tools and techniques, teams often find their ability to ship features slowing down over time.
- Refactoring vs. Rewriting: The talk emphasizes the difference between pushing for constant rewrites versus intentional refactoring to address performance changes and technical debt.
- Profiler Types: He explains the two profiler types—exact and sampling profilers—and their appropriate use cases in identifying performance bottlenecks. He presents code snippets illustrating how developers can implement profiling in Ruby applications effectively.
- Performance Reviews: Aaron shares his experiences derived from performance reviews, stressing the importance of targeting both runtime and memory management for optimizing applications.
- Garbage Collection: He dives deep into Ruby's garbage collector, explaining its dual role in allocation and freeing up memory, while detailing how to tune these settings to improve application performance.
- Memory Profiling: Aaron illustrates the use of object space and heap dumps for detailed memory profiling, culminating in a case study where he significantly reduced the memory footprint of a production application.
- Final Call to Action: He discusses the necessity of open-source performance improvement tools, emphasizing the role of community contributions to enhance developer productivity.

In conclusion, Aaron imparts the message that scaling Rails applications and enhancing performance should not only focus on the application itself but also nurture the development teams behind these applications. By leveraging profiling tools and best practices, developers can create efficient, high-performance applications while enjoying the journey of coding. The talk ends with a humorous anecdote about his home automation project, leaving the audience entertained yet enlightened about the technical aspects of Ruby on Rails.