Plaid Software Engineer Interview Guide

The first step in the Plaid Software Engineer interview process is a phone screen with a recruiter. During this call, they will ask you a series of questions to assess your experience, skills, and interest in the role.

It typically starts with the famous "tell me about yourself" question and goes on to discuss your professional background and any relevant experience or skills that make you a strong candidate for the role. The recruiter will also likely ask questions about your last projects or technical knowledge, for example, they may ask you to describe a particularly challenging project you've worked on in the past and how you approached it.

Note that candidates who have previous experience at top tech companies such the Uber Software Engineer or Google Software Engineer may have an advantage in the screening process. However, all candidates will be evaluated based on their skills and qualifications.

It's essential to come prepared for this call with a clear understanding of the company, your motivations for joining Plaid, and how your professional experiences make you the right fit for the role. Take the time to research the company and familiarise yourself with their products and services.

• Tell me about yourself
• Can you tell me about a particularly challenging project you've worked on in the past and how you approached it?
• Why are you interested in working at Plaid, and how do you think your experience and skills align with the requirements of the role?

This second round is a typical structures and algorithms (DS&A) round which includes two live coding questions. They are designed to assess your technical proficiency, problem-solving skills, and require a solid understanding of data structures and algorithms, such as graphs and max heaps

In addition to the live coding questions, you will be asked technical questions related to the Plaid Software Engineer role. These questions are designed to assess your knowledge of backend systems, API integrations, distributed systems, and large-scale system architecture.

The key to success in this round is to write clean, efficient, and scalable code, and demonstrate your ability to solve complex problems effectively.

1. Implement a graph traversal algorithm to find the shortest path between two nodes in a weighted graph.
2. Write a function that takes an array of integers and returns the kth smallest element in the array.
3. Design a distributed caching system that can handle a large number of requests and is fault-tolerant.

The final round of the interview process is a virtual final onsite round, which typically takes place around two weeks after the virtual technical interview. The virtual onsite consists of:

• Coding Interview
• System Design
• Behavioural Interview
• Coffee Chat

Coding Interview

The coding round is generally focused on testing your Data Structures and Algorithms skills. You will be presented with two DS&A style questions that will assess your ability to think critically and apply fundamental programming concepts to solve real-world problems. The questions are typically real-world problems that can be implemented using a HashMap. 

The initial prompt for the coding problem is usually fairly simple, but the interviewer may iterate on it and add more constraints or advanced concepts to make it more challenging. Therefore, during the 90-minute interview, you'll have to answer many follow-up questions from the interviewer.

The initial prompt for the coding problem is usually fairly simple, but the interviewer may iterate on it and add more constraints or advanced concepts to make it more challenging. Therefore, during the 90-minute interview, you'll have to answer many follow-up questions from the interviewer. It's best to practise with a mock interviewer or a Plaid Software Engineer to be prepared for the various turns this interview can take.

To give you an idea, here is a sample prompt: "You are given an array of integers, and you need to find two elements that add up to a specific target value. Write a function that returns the indices of these elements."

Potential follow-up questions:

• What is the time complexity of your solution?
• How would you optimise your solution for large arrays?
• Can you explain your code in more detail?
• How would you handle cases where there are multiple pairs of elements that add up to the target value?
• Can you identify any edge cases that your implementation doesn't handle?

It's best to practise with a mock interviewer or a Plaid Software Engineer to be prepared for the various turns this interview can take.

System Design

The system design interview is designed to assess your ability to design scalable and reliable systems. You will be asked to design a system that can handle a specific set of requirements, taking into account performance, scalability, and reliability. 

The questions are fairly straightforward and focus on assessing your understanding of API gateways, load balancers, queues, and relational/non-relational databases. As long as you have a basic understanding of these concepts, you should be well-prepared for this part of the interview. You should definitely check out a few more questions asked related to systems design before your interview.

Behavioural Interview

The behavioural interview is typically designed to assess your leadership abilities and teamwork skills. Plaid values collaborative, communication skills and a strong work ethic. 

During this interview, you will be asked questions related to your experience working in teams, managing time, and your leadership skills.

Coffee Chat

The coffee chat round is where you will have the opportunity to interact with a Plaid employee(s) and ask any questions you may have about the role or the company. You may want to ask questions about the company culture, the team structure, or the day-to-day responsibilities of a Plaid Software Engineer. 

For example, 

• What inspired you to join Plaid, and what has your experience been like so far?
• How would you describe the company culture at Plaid, and how does it support the work you do?
• What is the team structure like for the SWE team at Plaid, and how do you collaborate with other teams in the organisation?
• What are some of the biggest challenges you face as a Plaid Software Engineer?
• How does Plaid prioritise work and decide which projects to pursue?

1. "You are given an array of integers, and you need to find two elements that add up to a specific target value. Write a function that returns the indices of these elements."

Follow-up questions:

• What is the time complexity of your solution?
• How would you optimise your solution for large arrays?
• Can you explain your code in more detail?
• How would you handle cases where there are multiple pairs of elements that add up to the target value?
• Can you identify any edge cases that your implementation doesn't handle?
  
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• How would you design a system for a banking app that needs to handle millions of transactions per day while ensuring high availability and reliability?
• You are tasked with designing a system for a social media platform that can handle rapid user growth while maintaining fast response times. How would you approach this task?
• Design a system that can handle user authentication and authorization for a large e-commerce platform.
• How would you design a system for a ride-sharing app that needs to handle real-time location updates for drivers and passengers, while also ensuring data privacy and security?
• You are asked to design a system for a streaming media platform that can handle millions of concurrent users while minimising latency and ensuring high availability. How would you approach this task?

Again, be prepared for follow up questions to your original question, for example, if they ask you to design a credit system, you can expect questions like:

• How would you design a credit system that rewards users for responsible financial behaviour?
• Can you walk me through the steps you would take to design a credit system that promotes financial literacy?
• What are some potential challenges or limitations you would need to consider when designing a credit system, and how would you address them?

3. Behavioral Interview Questions

• Why Plaid?
• Tell us about a time when you had to work with a team to solve a difficult technical problem. What was your role, and how did you contribute to the team's success?
• Give an example of a time when you had to communicate a complex technical concept to a non-technical stakeholder. How did you ensure they understood the concept, and what was the outcome?
• Describe a situation in which you had to manage a conflict with a team member. How did you approach the situation, and what was the outcome?
• Give an example of a time when you went above and beyond to deliver a project on time or exceed expectations. What did you do, and what was the outcome?

You can check out the questions asked in the Amazon Software Engineer interview as well to be prepare better for this round.