Full-stack Engineer Interview

Can you describe your experience developing web-based and mobile software applications?

I have exprience working with mutiple project that use Rails as their primary BE framework, ReactJS for Web and Reactnative as application. I had oppotunities to hand on every aspects of the products.
Regarding the BE, We use rails to define the API, intereact with third party or database handle the integration, documenting the API through Swagger tool and use grapeAP as the API framework and integrate with Swagger to generate proper api document interface, we had Postgres as the database management. We also used Rspec and capybara to handle the unit tests and integration tests.
Regarding FE, we mainly used React and Typescript the develop FE pages, coorporate with designer to use our own Hero UI desgin which provided common components to use for the UI to understand the UI and develop a feature to intereact with BE based on BE API documents, I handled test by Jest
Regarding mobile app, which similar to the FE we used ReactNative, Typescript, Hero UI design systems and jest to cover test.
Luckily most of my task got deliver on time and got shout out from manger and clients

Your answer provides a solid overview of your experience with web-based and mobile software applications, showcasing a variety of technologies and practices. However, there are several areas for improvement.

First, ensure clarity and coherence. Instead of using "exprience" and "intereact," use "experience" and "interact." Proofreading will strengthen your professionalism. Second, try to organize your answer into clearer segments or bullet points to enhance readability.

You did well to mention specific technologies (Rails, ReactJS, React Native, Postgres, Swagger, etc.), which demonstrates your technical knowledge. However, it would be beneficial to include specific projects or challenges encountered, how you addressed them, and the impact your contributions had on the projects' success. This adds a narrative element that makes your response more engaging and memorable.

Additionally, while you referenced teamwork with designers and received positive feedback, elaborating on your collaboration skills or how you resolved any conflicts would showcase your soft skills too.

In terms of sufficiency, your answer covers relevant technologies, showcases hands-on involvement, and mentions testing methods, which are all crucial. Still, adding qualitative impacts on the projects or the user experience would strengthen it.

Overall, I would rate your answer 3.5/5. With a clearer structure, specific examples, and a deeper focus on your contribution and impact, your response could easily be enhanced to a 5/5.

What specific challenges have you faced when building applications using Ruby on Rails and React?

There were lot of challenge with the interact with the BE, there is the specific challenge that I remember was, we got the integration with the third party, which we need to sync all of the members infomation to the third parth, we got the issue of the response time took long time to process and some time it causes the timeout issue as I proactively monitor the web and see the response time was in warning zone, I took the task to investigate the issue. I found out that at the beggining we do the integration as the MVP so we just leave the web instance to handle the sync which is not good practice and we didn't aware of it because when we did the integration testing there were only one or two member within the organizations which normally fast.
The issue caused bad response time, occupied resource which the autoscale machinsm need to spin up most of the time
I come up with the proposal of bring it to the background job and FE handle it status by pooling mechanism. I got the approval from the manger and I successfully handled it .
The most challenging part was the FE need to know the current status of the syncing and we needed to show it to have better UX,and from the BE we need to smaller background job as wel, at the begining we followed the strategy of if this job done it will involke the next one and update status however it really hard to visualize it as we need to jump to the job and read the code however I got the idea of workflow which we can configure the flow of the jobs what it should run first and after, and we can easily see the flow configuration with a class so it really helpful.
I finished the development, document the implementation and give the comparation before and after implement the change, I got the recognition form the EM and the PO which boots me up

Your answer addresses the question effectively by highlighting a specific challenge you faced when integrating Ruby on Rails with React, particularly concerning third-party integrations and response time issues. You provide a clear narrative about identifying the problem, proposing a solution, and successfully implementing changes, which demonstrates your problem-solving and technical skills.

### Evaluation:
1. Clarity and Structure (3/5): While your answer contains relevant details, it could be clearer. Organizing it into distinct sections (challenge, investigation, solution, outcome) would enhance readability and understanding.

2. Technical Depth (4/5): You explain the technical challenges well, including the decision to use background jobs and a polling mechanism for the front end. However, providing more details about the specific technologies or tools you used (e.g., Sidekiq for background jobs) could add depth.

3. Outcome and Recognition (5/5): You conclude with a positive outcome, mentioning recognition from your manager and product owner, which effectively demonstrates the impact of your work.

### Improvement Suggestions:
- Be concise: Shorten some sentences for better flow. For example, instead of "there were lot of challenge with the interact with the BE," you could say, "I faced significant challenges interacting with the backend."
- Focus on relevant details: You could briefly mention how you monitored response times or specific metrics that indicated the problem, which would provide clearer context.
- Use bullet points: If appropriate in the interview format, bullet points could highlight key aspects of the challenge, solution, and outcome.

### Rating:
Your answer is solid, but could use some refinement. I would rate it 3.5/5.

How do you ensure scalability and security in your software applications?

Scalability Strategies
Architecture Design

Use microservices architecture to enable independent scaling of different components
Implement horizontal scaling with load balancers and auto-scaling groups
Design stateless applications where possible to make scaling easier
Use caching strategically (Redis, Memcached) to reduce database load
Implement database sharding or read replicas for data layer scaling

Performance Optimization

Use CDNs for static content delivery
Implement efficient database indexing and query optimization
Use asynchronous processing for heavy tasks (message queues like RabbitMQ or AWS SQS)
Monitor application performance with tools like New Relic or DataDog
Implement pagination and lazy loading for large datasets

Security Measures
Authentication & Authorization

Implement OAuth 2.0 or JWT for secure authentication
Use role-based access control (RBAC) with principle of least privilege
Enable multi-factor authentication for sensitive operations
Implement secure session management with proper timeouts

Data Protection

Encrypt data in transit (TLS/SSL) and at rest (AES-256)
Use environment variables or secure vaults for sensitive configuration
Implement proper input validation and sanitization to prevent injection attacks
Hash passwords with strong algorithms like bcrypt or Argon2

Infrastructure Security

Keep all dependencies and frameworks updated
Use Web Application Firewalls (WAF) to filter malicious traffic
Implement rate limiting and DDoS protection
Regular security audits and penetration testing
Use containerization with security best practices (Docker security scanning)

Monitoring & Compliance

Implement comprehensive logging and monitoring
Set up alerting for security incidents and performance issues
Follow compliance frameworks relevant to your industry (GDPR, HIPAA, etc.)
Regular backup and disaster recovery testing

Your answer is comprehensive and covers critical aspects of both scalability and security in software applications. You demonstrated a solid understanding of best practices in architectural design, performance optimization, data protection, and infrastructure security.

Evaluation:

1. Scalability Strategies: You effectively outlined key scalability techniques, like microservices architecture, horizontal scaling, and the use of caching. Mentioning load balancers and auto-scaling groups showcases your familiarity with cloud environments. Including database optimization methods adds depth.

2. Performance Optimization: You highlighted the importance of CDNs, database indexing, and asynchronous processing, which are essential for maintaining performance as traffic grows. Including monitoring tools indicates a proactive approach to performance management.

3. Security Measures: Your focus on authentication and authorization mechanisms, such as OAuth 2.0 and RBAC, shows that you understand the importance of securing user access. Data protection strategies like encryption, input validation, and secure password hashing are crucial for safeguarding data.

4. Infrastructure Security: You mentioned best practices for dependency management, WAFs, and rate limiting, which are central to defending against attacks. Your recognition of regular security audits reflects a commitment to ongoing security assessment.

5. Monitoring & Compliance: This section is vital, as ongoing monitoring and compliance are essential for both scalability and security. Your mention of logging, alerting, and adherence to regulations underlines a thorough approach.

Improvements:
- You might want to briefly address how to balance scalability and security, as they can sometimes conflict. For instance, briefly mention the need to prioritize security in microservices to maintain a decentralized approach.
- Consider including examples of specific tools or frameworks you've used in past projects to make your points more tangible and provide concrete experience.

Rating: 4.5/5. Your answer is well-structured and demonstrates a strong understanding of scalability and security, but could benefit from a few more personal insights or examples.