Amazon's site performance dropped. How would you investigate?

The interviewer with this question aims to gauge your problem-solving and analytical skills. They want to understand how you would go about identifying and resolving an issue related to site performance. When you answer, they want to see your knowledge and experience in handling such issues and your approach to process flow in problem-solving. The key parts to answer include:

1. Identifying the problem.
2. Gathering and analyzing data.
3. Seeking potential solutions.
4. Implementing and monitoring the solution.

When Amazon's site performance drops, firstly, I'd figure out the details of the problem. I'd engage with users if possible and use monitoring tools to understand more about the site's performance and where the issues lie.

Having gathered this information, the next step would be to analyze some critical metrics like server CPU usage, network latency, database response times, and more, to discover where the bottleneck is.

After identifying the problem, I would develop some potential solutions, which could involve optimizing the database, increasing server resources, modifying application code, and more.

Once the solution or solutions have been implemented, it's essential to continue to monitor the system's performance to ensure that the issue is resolved, and the site performance returns to normal. If not, I'll proceed with the next potential solution and repeat the process until the issue is fully resolved.

As a first step, I would profile the end-to-end user experience using Real User Monitoring (RUM) tools to understand where in the journey the latency or reduced performance is occurring. This tool captures and analyzes each transaction by users of a website or application. After identifying which parts of the site are performing poorly, I'd take a closer look into those areas.

Next, I'd analyze the problematic areas with more detailed tools, such as looking at server logs or using Application Performance Monitoring (APM) to understand what's happening in the backend.

Once the problem is identified, the next step would be to brainstorm potential solutions. For example, if the issue comes from the server-side, optimizing the server or upgrading it could be a remedy. If the problem lies within the app code, I would work with the development team to come up with a solution.

After implementing the solution, I would continuously monitor the performance, and based on the results, decide whether additional steps are necessary or if the solution was successful. It's important to keep retrying and refining using this approach until the problem is fully resolved.