The document provides tips for improving performance at Slack, including: 1. Monitoring performance to track existing and new codepaths and overall application performance. 2. Adding rate limits to APIs and jobs to prevent servers from overloading and spamming. 3. Paginating large lists to return data in chunks and reduce load. 4. Caching frequently accessed and expensive to calculate data locally, remotely, and in databases. 5. Making tasks asynchronous by splitting them into subtasks processed in parallel or via job queues. 6. Having a tiered degradation plan to determine priority of features during outages.