Senior Engineer Interview

Can you describe your experience with Ruby on Rails and Python in backend development?

I have over 6 years of experience in Ruby and Rails,. During my career, I've worked with four companies that all used Rails as their primary backend framework across various industries including logistics, human resources, and healthcare. I have extensive experience optimizing web performance, improving background job which is sidekiq efficiency, and tuning database queries—particularly in PostgreSQL.
I also have a solid foundation in containerization, AWS services and Linux.
I'm also familiar with Sidekiq for background job , ActiveRecords Object relation mapping, Cancancan authorization, Rspec and capybara for Testing
I don't have much experience with Python within production environment however Im a fast learner so I can learn about how it work

Your answer is a solid starting point for discussing your experience with Ruby on Rails and Python in backend development. It effectively highlights your extensive experience with Ruby on Rails, emphasizing specific skills and technologies that are relevant to the role. You effectively cover different areas of expertise, including performance optimization and background job management.

However, there are areas for improvement, particularly in how you present your Python experience and your ability to adapt. Instead of merely stating a lack of experience in Python, consider mentioning any relevant projects or personal initiatives that demonstrate your familiarity with the language or its frameworks. This would make your experience feel more well-rounded and show your proactive approach to learning.

Additionally, you might want to include specific achievements or projects that illustrate your contributions to your past companies. Mentioning measurable outcomes (e.g., “reduced query time by 40%” or “increased background job processing efficiency by 30%”) can significantly enhance your credibility.

In summary, while your answer addresses the question and conveys your strengths, it could benefit from showcasing your adaptability and providing quantifiable achievements. I would rate your answer 3.5/5. To improve, focus on building a narrative that includes triumphs in your roles, an eagerness to learn Python effectively, and a demonstration of problem-solving abilities that transcend your primary expertise.

How do you approach API design to ensure scalability and performance?

In my current role, I'm the one who in charge of scalability from the web instance and web instance performance, coordinate with devops team to handle the optimizing autoscale and load balancing for the app.
My approach is following the restful principle to develop api which should be clear among the BE and FE team, Apply the best practice in term of maximum response time for the endpoint to the proper query plan prevent some of common mistake such as: missing database query index, n+1, duplicated rendering, web instance handle heavy job
we also developed a monitoring page which would proactively send notification if it detects the bad performance endpoint
update puma configuration the improve the availibility within the web instance
Make sure all of the changes within the app that have tests with 80% code coverage

Your answer demonstrates a solid understanding of backend performance and scalability, but it can be refined for clarity and depth.

Strengths:
1. Collaboration: You highlight the importance of working with the DevOps team, which shows that you value cross-functional teamwork in managing scalability.
2. RESTful Principles: Mentioning the RESTful approach indicates a fundamental understanding of API design, ensuring clarity between backend and frontend teams.
3. Performance Considerations: You address common performance pitfalls like missing database indexes and N+1 query problems, which showcases your technical knowledge.
4. Monitoring: The proactive approach in developing a monitoring system to notify on performance issues is excellent and indicative of a forward-thinking mindset.
5. Testing: Mentioning the necessity for code coverage reinforces the importance of maintainable and reliable code.

Areas for Improvement:
1. Structure and Clarity: Your response could be more structured. Start with principles of design, touch on monitoring, and then discuss testing strategies to convey a logical flow.
2. Scalability Techniques: You could expand on specific techniques for scaling APIs, like caching strategies (e.g., Redis), rate limiting, or using pagination.
3. Performance Metrics: Discussing how you measure performance, such as using metrics like response times and throughput, would add depth.
4. User Experience: Addressing how API design affects user experience could illustrate a broader perspective on performance.

Rating: 3.5/5

Improvements could include expanding on scalability techniques, discussing performance metrics, and providing a clearer structure to your response for a more persuasive presentation.

Can you provide an example of a complex technical problem you solved in a previous role?

In my current role, we have a feature that allow user to submit the preadmission form. and we will send the form as the PDF. Since the form module needs some javascript invole to handle the the dynamic fields. So we use Chromium to handle the machinsm as it support export pdf and support pretty much javascript library. the issue we have is that as you know the preadmission form normally require a your signature and we need to show that signature within the pdf. however we got the issue that only happened on production that the pdfs sending to clinicals didn't include the signature or any images there. I need to investigate the issue, as it was only happening on production, at that time I was thought that the issue simply because of the chromium version and figureout it's however the pilost twist is there are 2 versions of the chromium in the server and the apt doesn't work properly however the snap work well, as the quick fix I updated the env to use the snap version however there is another huge issue there since the production server isn't match with the staging one the staging one is using latest ubuntu version however the produciton is using 20.04(this was because of the person who handle the server left and no document relating to it so the team and no one aware of the issue ) which is not good as we need to be consistent among the environment, and we temporary upgrade the server, and I come up with the Dockerizing approach which bring a lot of benefits, I wrote down the proposal, mention about the pros and cons, show the example of how to use on local and my own server.
the result , the company only decide to go with the development approach and keep my proposal to review for staging and production. it significantly improved the development environment setup

Your answer demonstrates a solid understanding of a complex technical problem and illustrates your problem-solving capabilities in a specific context. You described a real-world issue involving the rendering of a signature in a PDF generated from a dynamically-generated form, which is relevant to backend development. The investigation process, identifying discrepancies in the environments, and ultimately proposing a strategic solution such as Dockerization show initiative and a focus on long-term improvements.

However, there are several areas to improve. First, clarify the problem more succinctly at the beginning to ensure that the interviewer is immediately engaged. Instead of diving into the specifics too quickly, briefly summarize the challenge before discussing how you approached it. Also, the explanation about the server discrepancies could be simplified to emphasize the importance of environment consistency.

Further, it would help to quantify the impact of your solution—did the Docker approach reduce deployment times, improve reliability, or simplify development for your team? Including a specific metric or outcome would strengthen your answer. Lastly, ensure that terminology (e.g., “apt” vs. “snap”) is accurate and clear for someone less technical.

Overall, I would rate your answer 3.5/5. It showcases a relevant problem-solving scenario but could benefit from improved clarity, structure, and quantifiable outcomes. Focus on enhancing these aspects for a more compelling response.