JPMorgan Chase Application Security Engineer Interview Experience at Nextdoor

I recently interviewed for the Application Security Engineer position at Nextdoor, and I want to share my experience to help others who may be interviewing for a similar role. The process was comprehensive, focusing on both my technical expertise in application security and my ability to collaborate with cross-functional teams. Below is a detailed breakdown of my interview experience, including the various stages of the process, the types of questions I encountered, and tips for preparation.

Interview Process Overview

The interview process for the Application Security Engineer position at Nextdoor typically consists of the following stages:

1. Initial Screening (HR/Recruiter Call)
2. Technical Interview 1: Security Knowledge and Problem-Solving
3. Technical Interview 2: Real-World Security Scenario/Case Study
4. Behavioral Interview
5. Final Round: Team Fit and Leadership Discussion

Stage 1: Initial Screening (HR/Recruiter Call)

The first stage was an HR/recruiter screening call, which lasted about 30 minutes. This call was mainly focused on my background, why I was interested in the Application Security Engineer role at Nextdoor, and my overall fit for the position.

Key Topics Discussed:

• Why Nextdoor?
  I explained that I was excited about Nextdoor’s mission to bring neighbors together and foster community engagement. I highlighted the opportunity to contribute to the security of a platform that holds personal and sensitive data for millions of users. Additionally, Nextdoor’s innovative approach to scalable systems and cloud-based solutions was something I was keen to be a part of.

• Security Experience:
  The recruiter asked about my previous experience in application security, particularly in areas like code review, vulnerability management, and penetration testing. I shared examples where I identified and remediated security flaws, implemented security best practices, and worked with development teams to integrate security into the development lifecycle.

• Role Understanding:
  I explained my understanding of the Application Security Engineer role, which involves conducting security assessments, penetration testing, collaborating with the engineering teams to ensure secure coding practices, and developing tools to automate security processes.

• Salary and Availability:
  We discussed salary expectations, the interview process timeline, and my availability to start the position.

This call helped the recruiter assess if my qualifications and interest aligned with the role’s needs.

Stage 2: Technical Interview 1 – Security Knowledge and Problem-Solving

The first technical interview was focused on my security knowledge and ability to solve real-world application security problems. The interviewer, who was a senior Security Engineer, asked a mix of theoretical questions and hands-on coding challenges.

Example Questions and My Responses:

• What are the top OWASP vulnerabilities, and how would you mitigate them in a web application?
  I explained the OWASP Top 10 and provided specific examples of how to mitigate each vulnerability. For example, for SQL Injection (A1), I discussed how using prepared statements and parameterized queries could prevent attackers from injecting malicious SQL code. For Cross-Site Scripting (XSS) (A7), I talked about sanitizing user inputs and employing Content Security Policy (CSP) headers.

• How would you secure an API?
  I discussed the importance of authentication and authorization in securing an API. I recommended using OAuth 2.0 for secure, token-based authentication and JWT (JSON Web Tokens) for stateless sessions. I also mentioned enforcing rate-limiting, input validation, and CORS (Cross-Origin Resource Sharing) configuration as key measures to protect APIs from abuse.

• Code Review for Security Vulnerabilities:
  I was given a short code snippet and asked to review it for security vulnerabilities. The code contained common flaws such as unvalidated user input, insecure data storage, and potential race conditions. I identified these issues and suggested best practices like input sanitization, hashed passwords with bcrypt, and thread-safe operations to mitigate these vulnerabilities.

This round assessed my technical expertise in application security and my ability to identify and solve real-world security issues.

Stage 3: Technical Interview 2 – Real-World Security Scenario/Case Study

The second technical interview involved a real-world security scenario or case study. I was presented with a security challenge that required me to design a solution to mitigate risks and protect the system from threats.

Case Study Scenario:

Scenario:
“Nextdoor has recently launched a new feature where users can post classified ads. However, there have been reports of malicious content being posted, including phishing links, malware, and spam. How would you approach securing this feature?”

Response:

1. Initial Risk Assessment:
   I started by identifying potential risks, such as user-generated content being exploited for phishing attacks, malware distribution, or spam. I discussed how these risks could harm users’ trust in the platform and violate security policies.

2. Input Validation and Filtering:
   I emphasized the importance of input validation and content filtering to prevent malicious content. I suggested using regular expressions to filter out known malicious patterns, blacklists to identify harmful URLs, and whitelists to ensure only safe content is allowed. For HTML content, I recommended using libraries like OWASP Java HTML Sanitizer to remove potentially dangerous elements like <script> tags.

3. User Authentication and Permissions:
   To prevent unauthorized users from posting malicious content, I proposed implementing strong user authentication (e.g., MFA - Multi-Factor Authentication) and granular user roles to ensure only trusted users can post ads. This would reduce the risk of fake accounts posting harmful content.

4. Monitoring and Reporting:
   I also discussed implementing real-time monitoring and machine learning algorithms to detect abnormal posting behavior or patterns indicative of malicious activity. Additionally, I suggested incorporating a reporting mechanism where users can flag suspicious content, which would be reviewed by the moderation team.

5. Incident Response Plan:
   I recommended having a clear incident response plan to quickly address any security incidents, including the removal of harmful content and communication with affected users.

This round tested my ability to apply security best practices to real-world scenarios and assess how to protect a platform from various cyber threats.

Stage 4: Behavioral Interview

The behavioral interview was focused on assessing my soft skills, communication, and how well I would fit into Nextdoor’s team culture. The interviewer asked about my ability to collaborate, lead teams, and approach challenges in a dynamic environment.

Example Questions and My Responses:

• Tell me about a time you faced a difficult security challenge and how you overcame it.
  I shared an example from a previous role where I had to address a zero-day vulnerability that was discovered in one of our public-facing applications. I explained how I quickly gathered the relevant stakeholders, analyzed the vulnerability, and implemented a patch before it was publicly exploited. I emphasized the importance of team collaboration and rapid response in high-pressure situations.

• How do you communicate security risks to non-technical stakeholders?
  I explained that I focus on simplifying complex concepts by relating them to the business impact. For example, I might explain how a particular vulnerability could lead to data breaches or reputation damage, and what actions we’re taking to mitigate that risk. I also emphasized using visual aids and real-world examples to make my explanations more accessible.

• How do you stay up-to-date with the latest security trends and threats?
  I discussed my proactive approach to staying updated, including reading security blogs (e.g., Krebs on Security), attending security conferences, and participating in online communities (e.g., Reddit’s /r/netsec). I also mentioned my involvement in capture the flag (CTF) competitions, which helps me hone my skills in a practical, hands-on manner.

This round assessed my communication skills, teamwork, and ability to handle complex security challenges in a collaborative environment.

Stage 5: Final Round – Team Fit and Leadership Discussion

The final round was with senior leadership and was focused on assessing my strategic thinking, leadership potential, and how well I would fit within Nextdoor’s culture.

Key Questions:

• How do you approach leading a security team?
  I explained my approach to leadership, which involves empowering team members, setting clear goals, and fostering a culture of continuous learning. I also mentioned the importance of knowledge sharing and encouraging team members to participate in security research and training opportunities.

• What role do you think security plays in the development lifecycle at Nextdoor?
  I emphasized the importance of shifting security left by integrating security practices early in the development process. This includes conducting regular code reviews, performing static analysis, and implementing secure coding guidelines. I also highlighted the need for collaboration between DevOps, engineering, and security teams to ensure that security is embedded in every stage of the development lifecycle.

• Where do you see the future of application security in the next 5 years?
  I discussed the increasing importance of automation in application security, particularly with DevSecOps. I predicted that AI and machine learning would play a larger role in detecting threats and vulnerabilities in real-time, helping security teams be more proactive rather than reactive.

Key Takeaways and Tips for Preparation

1. Application Security Knowledge: Be prepared to discuss security best practices, such as OWASP Top 10, secure coding principles, and how to protect applications from common vulnerabilities.

2. Real-World Problem Solving: Practice answering case study questions where you need to design security solutions for specific scenarios. Focus on risk assessment, mitigation strategies, and client-focused solutions.

3. Communication: You will be expected to explain complex technical concepts to both technical and non-technical stakeholders, so practice simplifying your explanations without losing the essential details.

4. Behavioral Questions: Use the STAR method (Situation, Task, Action, Result) to answer questions about your past experiences, particularly in handling security incidents and working in cross-functional teams.