Serko Software Engineer Interview: Questions, Experience & Prep (2026)

Serko builds corporate travel and expense management software used by enterprises across the Asia-Pacific region and globally. The company is publicly listed and has a growing engineering team with a strong focus on cloud-native development.

As of July 2026, Serko has 2 Software Engineer roles open. Candidates report that the interview process typically involves a recruiter screening call, a technical assessment, and one or more panel discussions covering both coding and system design.

The focus areas reflect Serko's product: API design, cloud services, third-party travel provider integrations, and building reliable systems that handle real-time bookings and expense data at scale.

These questions appear frequently in what candidates report for travel tech and SaaS engineering roles.

1. Walk us through how you would design a REST API for a corporate travel booking system.
2. How have you handled a situation where a third-party API integration failed in production?
3. Describe a time you improved the performance of a system under heavy load.
4. How do you approach testing when your code depends on external travel provider APIs?
5. What cloud platform experience do you have (AWS, Azure, or GCP), and how have you applied it in a past project?
6. How would you ensure data consistency when multiple microservices are involved in a single booking transaction?
7. Tell us about a time you worked closely with a product manager to deliver a feature under a tight deadline.
8. How do you handle technical debt: do you address it as you go, or schedule dedicated time?
9. Describe your experience with event-driven architecture or message queues.
10. How would you debug a performance bottleneck in a live application without causing downtime?
11. Tell us about a project where you had to learn a new technology quickly and apply it to a real problem.
12. What do you look for in a code review, and how do you give constructive feedback?

Q: How have you handled a third-party API integration failing in production?

*Situation:* At my previous company, we integrated with a third-party hotel inventory API. One evening, the external provider went down during business hours, breaking our booking flow for a large number of active users.

*Task:* I was the on-call engineer. My job was to isolate the failure, keep our own service healthy, and communicate clearly to the team.

*Action:* I confirmed the failure was on the provider's end by checking their status page and our own error logs. I added a circuit breaker around that API call so our system would fail gracefully and show a user-friendly message instead of crashing. I also set up a Slack alert tied to the provider's recovery webhook so we would know the moment they came back online.

*Result:* Our core service stayed up throughout the outage. Booking flow resumed automatically once the provider recovered. We later added that circuit-breaker pattern as a standard for all external integrations.

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Q: Describe a time you improved system performance under heavy load.

*Situation:* Our expense reporting module was timing out for large corporate clients who submitted thousands of transactions at month-end.

*Task:* I was asked to investigate and reduce the response time to an acceptable level before the next billing cycle.

*Action:* I profiled the database queries and found that a report-generation query was doing a full table scan because of a missing compound index. I added the index, moved the heavy aggregation to a background job, and returned a 'report in progress' status to the UI instead of blocking the request.

*Result:* Month-end report generation went from timing out to completing quickly for most clients. The product team was able to remove a longstanding 'known issue' note from the help docs.

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Q: Tell us about a project where you had to learn a new technology quickly.

*Situation:* My team was migrating our monolith to a microservices setup on Kubernetes, a platform none of us had used in production before.

*Task:* I volunteered to own the first service migration and figure out our deployment pattern so the rest of the team could follow it.

*Action:* I spent the first week going through official Kubernetes documentation and a focused online course. I then set up a sandbox environment, migrated one low-risk service, and wrote an internal runbook covering deployment, rollback, and health checks.

*Result:* The migration went live without incidents. My runbook became the template for the following service migrations, which the rest of the team completed in roughly half the time.

STAR (Situation, Task, Action, Result) is the most useful framework for behavioral questions. Keep the Situation and Task brief (two or three sentences), spend most of your time on the Action (what you specifically did), and close with a concrete Result.

For technical and design questions, candidates report that Serko interviewers appreciate a structured approach:

• Clarify requirements and constraints before jumping to a solution.
• Talk through trade-offs out loud rather than jumping to one answer.
• Relate your design choices back to the product context (travel data, real-time availability, compliance).
• Show awareness of failure modes: what happens if a third-party API is slow, or a message queue backs up?

For coding rounds, think aloud as you write. Interviewers typically want to see how you reason, not just whether you reach the right answer. Mention edge cases, talk about time and space complexity, and ask before assuming anything about the inputs.

Candidates report that Serko interviewers care about several things beyond raw coding ability.

Comfort with integrations. Serko's platform connects to airlines, hotels, expense systems, and corporate directories. Engineers who have worked with unreliable external APIs and know patterns like circuit breakers, retries, and idempotency tend to stand out.

Cloud and infrastructure awareness. Most of Serko's stack is cloud-hosted. You do not need to be a DevOps specialist, but knowing how your code behaves at scale and how to use cloud services sensibly matters.

Product empathy. Interviewers appreciate candidates who think about the end user, whether a corporate travel manager or a business traveller filing expenses, not just the technical spec.

Clear communication. Engineering at Serko is collaborative, spanning multiple time zones and countries. Candidates who can explain complex decisions simply, and who listen well in discussions, are valued.

Ownership mentality. Be ready to talk about incidents you have handled, bugs you caught before they shipped, and times you improved a process without being asked.

One to two weeks before your interview:

• Review Serko's products (Serko Online and the Zeno expense platform) so you can connect your experience to their domain during answers.
• Brush up on REST API design: HTTP status codes, pagination, versioning, and error handling.
• Revise at least one cloud platform you have used. Focus on managed services such as queues, storage, and managed databases rather than low-level networking.
• Prepare two or three STAR stories covering: a production incident, a performance improvement, and a cross-team collaboration.

In the days before:

• Do a couple of timed coding exercises on a platform you are comfortable with. Focus on arrays, hash maps, and basic graph problems, which commonly appear in SaaS engineering interviews.
• Prepare two or three questions to ask the interviewer. Good options: 'How does your team handle on-call?' or 'What does a typical sprint look like for this team?'

On the day:

• For design questions, ask clarifying questions first. Do not start drawing boxes immediately.
• For coding questions, think aloud. Silence makes it hard for the interviewer to help if you are stuck.
• Keep your STAR answers under three minutes each.

Jumping to a solution without clarifying. For system design and API questions, candidates who dive in without asking about scale, SLAs, or constraints often design something that does not fit the actual problem.

Vague STAR answers. Saying 'we improved performance' without a concrete result leaves the interviewer with nothing to evaluate. If you do not have exact numbers, describe the qualitative change clearly.

Ignoring failure scenarios. In a travel tech context, third-party systems go down. Candidates who design for the happy path only, and do not mention retries, fallbacks, or alerts, miss a key signal interviewers look for.

Not asking questions. Candidates report that Serko interviewers treat 'do you have any questions?' as part of the evaluation. Saying 'no, I think I am good' can read as low engagement.

Over-engineering answers. Proposing a complex distributed system when a simpler design would work signals poor judgment. Start simple, then add complexity only when you can justify it.

Underselling ownership. Many candidates say 'the team did X' when they should say 'I did X, and here is how.' Interviewers want to understand your personal contribution.