Are you about to interview for a Full Stack or Backend Engineer position at Wise? If yes, you’re reading the right blog. Here’s a handy guide to help you prepare for our technical interview.

The Wise technical interview dives deep into two main areas: 
1. Who you are as a developer and your technical skills that are relevant to the role
2. How experienced you are in system design - designing a performant, easy to maintain and extensible system to solve real-world problems.

The interview comprises two parts: a discussion about your experience with some technical questions and a technical (system design) task. 

The interview typically lasts about an hour and a half, with the system design task taking up the majority of this time.

You’ll receive an email from Wise containing the details of the interview: when it’ll happen, who’ll the two engineers be and how it’ll be conducted. It can be an onsite interview where you get the opportunity to visit one of our offices (depending on your location), or a video interview via Zoom.

Our interviewers will provide a quick introduction of themselves and tell you about their roles in Wise.

Then we’ll inquire about you – your projects, technical achievements and what you have worked on.

For the design task, we will present a product task or problematic area and we expect you to propose a high-level architecture approach. Additionally, we may also ask for further details and delve into lower-level aspects such as defining data structures, or clarifying a specific logic to cover usage scenarios.

Previous experience section

During the interview, expect some questions about your past experiences and projects. We would recommend to take a moment before the interview to consider:

• Your contributions to projects you’ve worked on and your role in the projects, what decisions you have taken
• Recent bugs you’ve fixed, problems you’ve solved and tech you’ve contributed towards
• Be prepared to use a whiteboard (we use Hackerrank) to communicate your thoughts effectively

For some engineering positions (for example iOS/Android), candidates may be asked to complete a take-home coding problem prior to the interview. If this applies to you, be prepared to walk us through your solution and thought process.

System design questions and task section

We won’t ask questions that are only found in university textbooks. Our focus lies more on practical application and understanding rather than memorization of certain concepts. We are not looking for the “right” answer, rather, we aim to solve problems and encourage you to articulate your thought process so that the interviewers understand your reasoning. Nevertheless, we encourage you to review the following technical topics: 

• General software development life cycle topics
• SOLID principles, design patterns
• Microservices: designing, development, deployment, tracing, and monitoring
• Distributed systems, transactions
  
• Sync/async communication between services, client-service communication, eventual consistency
  
• Product thinking: As “product engineers” at Wise, we need to think from the customer’s perspective and understand the product needs - incorporate these considerations into your own design
  
• Problem solving: Your approach to solving a non-trivial problem within a set time and arriving at a working solution
  
• Communication: Your collaboration style in problem-solving as well as your ability to justify your decisions. We want to understand why you approach problems a certain way, how you design solutions and your openness to feedback
  
• Technical proficiency: Your level of knowledge in technical subjects that are relevant to Wise’s technical stack as well as those necessary for discussing and developing system designs
  
• Scalability and availability of your solution
  
• Testing and monitoring: Your strategy for instrumenting and observing services
  
• Error handling: Your approach to preparing the system for expected and unexpected errors
  
• Data storage/Databases
  

Additionally, don’t forget common algorithms and data structures – understanding their usage, complexity and general functionality. While we won’t expect you to implement a red-black tree, comprehending the complexity of data insertion can be beneficial. 

You might also want to review role-specific topics if you’ve applied for a specific position. For example, if you are applying for our security team, take some time to cover security related topics in your preparation. Similarly, streaming-related roles should anticipate deeper questions around streaming technologies, and so forth.

When approaching any technical task, we suggest the following: 

• Make sure you fully understand the question. If you are uncertain, don’t hesitate to ask for clarification.
• Begin with a simple solution and iterate to improve it. If time runs short, just explain to us how you would improve it. However, it is also acceptable to start with the best solution right away :)
• Talk us through your thought process and assumptions as you tackle the problem

Feel free to ask the interviewers for help - they are there to support you in completing the task and demonstrating your problem-solving abilities. 

• For remote interviews, a stable internet connection and a quiet environment are very important. Consider using a headset for better audio quality for both yourself and the interviewers.
• We recommend joining the interview via video, not just audio to establish clearer communication and reduce misunderstandings. 
• Since you will be tasked with system design, having access to a computer is essential.
• Be ready to use an online collaborative whiteboard tool (e.g. Hackerrank).

Finally, at the conclusion of the system design interview at Wise, you will have the opportunity to ask questions. Whether about life at Wise, our global money transfer operations, or our technology stack, feel free to ask.

Good luck!