Frontend Fundamentals: Top 10 Interview Questions and In-Depth Answers for Every Developer

Coding Interview Questions

These are some questions that can be asked in coding interviews to assess a developer's skill level and ability to solve practical problems.

1. Preventing Concurrent Editing of Articles

Question:

Suppose you are implementing a journal editing system where editors can edit articles in the admin panel. How would you prevent two editors from simultaneously editing the same article and overwriting each other's changes?

Answer

Use optimistic locking or pessimistic locking mechanisms to ensure that only one editor can modify an article at a time.

2. Principles of Zero Downtime Deployment

Question:

What are the principles of zero downtime deployment, an approach that deploys an application without service downtime? How is this achieved?

Answer

Key principles of zero downtime deployment include:

Blue-green deployment: Use two identical production environments, swapping between them during deployment.
Feature flagging: Gradually roll out new features by controlling their visibility with feature flags.
Canary releasing: Deploy new code to a small subset of users first, monitoring for issues before wider rollout.

3. Criticisms of Your Preferred Framework

Question:

Name aspects of your preferred framework that you dislike or that don't work the way you'd like. Explain how and where these issues arise and how they could be improved.

Answer

Be honest about the limitations of your chosen framework, providing specific examples and suggestions for improvement.

4. Handling Long-Running Cron Jobs

Question:

What could happen if your cron job, which runs every minute, starts taking more than one minute to execute? How can this be prevented?

Answer

Potential issues include missed executions and cascading failures. Consider breaking down the task into smaller chunks, optimizing code, or using a queueing system.

5. Denormalizing Data in Databases

Question:

Have you ever encountered the need to denormalize data in a database? If so, what problem were you trying to solve, what challenges did you face, and how could it have been done better?

Answer

Explain the specific situation where denormalization was necessary, the trade-offs involved, and potential alternatives.

6. Mocking External Calls in Tests

Question:

If you write tests, how do you circumvent the issue of external calls made by the code you're testing? Consider the scenario where external calls are prohibited on CI (continuous integration). Why is this a good practice?

Answer

Discuss techniques like mocking, stubbing, and dependency injection to isolate tests from external dependencies. Explain the benefits of avoiding external calls in CI environments.

7. Synchronizing Email Changes with External Systems

Question:

Suppose your system implements email change functionality. However, the email is also stored in an external system, such as a payment processor, which sends emails to users (but users don't directly interact with it). How would you implement email synchronization with the external system?

Answer

Outline a strategy for synchronizing email changes, considering options like polling, webhooks, or message queues.

8. Discovering Production Errors

Question:

How do you learn about errors that occur in production? Do you rely on user reports or have automated mechanisms in place?

Answer

Describe your approach to error monitoring and reporting, emphasizing the use of tools and techniques for proactive error detection and alerting.

9. Designing a Simple Chat Application

Question:

How would you design a simple chat application? You can ask the backend engineer about the backend part and the frontend engineer about the frontend part. There could be many branches in this conversation.

Answer

Break down the chat application into its components (backend, frontend, database) and explain the interaction and data flow between them.

10. Isolating Tests in a Multi-User Environment

Question:

How is test isolation ensured when multiple tests run concurrently and access the database, potentially modifying it? If your framework doesn't provide isolation, how would you implement or improve it?

Answer

Discuss mechanisms like transactions, rollbacks, or test databases to ensure data integrity and prevent conflicts during concurrent test execution.

Additional Tips:
Encourage the candidate to elaborate on their thought process and reasoning behind their answers.
Assess their problem-solving skills, ability to think critically, and knowledge of relevant technologies.
Gauge their communication and collaboration skills throughout the interview.