As a Software Engineer at Censys, you will play a pivotal role in developing and maintaining critical software systems that underpin the company's mission of enhancing internet security and visibility for its users. This position is integral to the design and implementation of scalable backend services that process and analyze vast amounts of data, ensuring that Censys can deliver accurate and timely information to its customers. You will work on innovative projects that leverage cutting-edge technologies, collaborating with cross-functional teams to deliver solutions that enhance the performance and reliability of Censys products. Your contributions will directly impact users by providing them with enhanced insights into cybersecurity threats and vulnerabilities. This role presents an exciting opportunity to tackle complex challenges, drive significant business outcomes, and influence the strategic direction of the company.
Initial Screening
reportedThe first step involves a review of your application and a preliminary discussion about your background.
What to demonstrate
- The first step involves a review of your application and a preliminary discussion about your background
- Depth in Kubernetes (K8s)
How to prepare
- Be able to walk your CV end to end in two minutes, and say why this company specifically.
- Have your salary expectations, notice period and location constraints ready, and ask for the rest of the loop in writing.
Technical Assessments
reportedCandidates will undergo technical evaluations to assess their relevant skills and knowledge.
What to demonstrate
- Candidates will undergo technical evaluations to assess their relevant skills and knowledge
- Depth in Kubernetes (K8s)
How to prepare
- Answer aloud and timed: Can you explain the differences between SQL and NoSQL databases?
- Answer aloud and timed: Describe a challenging technical problem you faced and how you resolved it.
Interviews with Team Members
reportedEngagement with various team members to evaluate both technical skills and cultural fit.
What to demonstrate
- Engagement with various team members to evaluate both technical skills and cultural fit
- Depth in Kubernetes (K8s)
How to prepare
- Answer aloud and timed: What tools and methodologies do you use for debugging and testing your code?
- Answer aloud and timed: How would you approach designing a system to handle millions of concurrent users?
PracHub editorial advice for the preparation topics above.
Clarify Expectations
Always seek to understand the role and expectations clearly during your interviews. Asking insightful questions can demonstrate your interest and engagement.
Showcase Collaboration
Highlight experiences where you worked effectively with others, as teamwork is highly valued at Censys.
Be Prepared for Technical Depth
Expect to dive deep into technical topics, so ensure you can discuss your past work and projects in detail.
Express a Growth Mindset
Demonstrate your willingness to learn and adapt, as Censys values continuous improvement.
Choose a category, try a prompt, then open its approach, worked solution or follow-up when you need it.
How would you approach designing a system to handle millions of concurrent users?
How would you approach designing a system to handle millions of concurrent users?
Approach
- Say what the runtime actually does before reasoning about the code.
- Name what is shared across threads and what owns each piece of state.
- Identify the window where an invariant is briefly untrue.
- Distinguish a value from a reference to it, and say which one you handed out.
Follow-up
- What happens if two callers reach this at the same time?
- Where could this allocate more than you expect?
Write a function to reverse a linked list.
Write a function to reverse a linked list.
Approach
- Restate the input: its shape, its size, and what is guaranteed about it.
- Name the brute-force solution and its complexity before improving on it.
- Choose the data structure from the access pattern, not from familiarity.
- State the target complexity and say which constraint rules the naive version out.
Follow-up
- How does this change if the input no longer fits in memory?
- What is the worst case, and how likely is it on real data?
How would you implement an algorithm to find the shortest path in a graph?
How would you implement an algorithm to find the shortest path in a graph?
Approach
- Restate the input: its shape, its size, and what is guaranteed about it.
- Name the brute-force solution and its complexity before improving on it.
- Choose the data structure from the access pattern, not from familiarity.
- State the target complexity and say which constraint rules the naive version out.
Follow-up
- How does this change if the input no longer fits in memory?
- What is the worst case, and how likely is it on real data?
Can you explain Big O notation and provide examples of its use?
Can you explain Big O notation and provide examples of its use?
Approach
- Restate the input: its shape, its size, and what is guaranteed about it.
- Name the brute-force solution and its complexity before improving on it.
- Choose the data structure from the access pattern, not from familiarity.
- State the target complexity and say which constraint rules the naive version out.
Follow-up
- How does this change if the input no longer fits in memory?
- What is the worst case, and how likely is it on real data?
Can you explain the differences between SQL and NoSQL databases?
Can you explain the differences between SQL and NoSQL databases?
Approach
- Name the grain you start from and join outward from it.
- Check whether any join is one-to-many before aggregating, or the sums inflate.
- Say which index the query would use, and what makes it unusable.
- Handle the rows that do not match: that is usually the actual question.
Follow-up
- How does the query change if that join becomes one-to-many?
- What happens to this when the table is ten times larger?
Find version gaps and relay lag with window functions
outbox_event holds event_id, aggregate_type, aggregate_id, aggregate_version, event_type, payload, status ('pending','published','dead'), attempts, created_at, published_at. A projection is missing rows and you must decide whether the relay skipped events or the consumer dropped them. Write three queries over the last seven days: one listing every aggregate_id whose published aggregate_version sequence has a hole, one giving per-day counts with a running total, and one returning the newest published event per aggregate. For each, say where the window function is evaluated relative to WHERE and LIMIT. PostgreSQL 16.
Approach
- Gaps: compute lead(aggregate_version) OVER (PARTITION BY aggregate_id ORDER BY aggregate_version) in a subquery, then filter next_version <> aggregate_version + 1 in the outer query. Window functions are evaluated after WHERE, GROUP BY and HAVING and before the outer ORDER BY and LIMIT, so the predicate cannot sit in the same WHERE clause and PostgreSQL 16 has no QUALIFY.
- Say what the seven-day filter does to the answer: it truncates every partition, so the first row per aggregate has no predecessor inside the window and a hole spanning the boundary is invisible. Widen the window, or join to resource.version as the authority for the true maximum.
- Running total: SELECT date_trunc('day', created_at) AS d, count() AS n, sum(count()) OVER (ORDER BY date_trunc('day', created_at) ROWS UNBOUNDED PRECEDING). An aggregate inside a window call is legal because grouping runs before windowing. The grouping key is unique per row here so ROWS and RANGE agree, but write the frame anyway — over ungrouped rows with tied timestamps the default RANGE frame pulls in every peer row and the total jumps.
- Newest per aggregate: DISTINCT ON (aggregate_id) ... ORDER BY aggregate_id, aggregate_version DESC is the cheap PostgreSQL-only form when an index matches that order; row_number() OVER (PARTITION BY aggregate_id ORDER BY aggregate_version DESC) = 1 is the portable form and needs a subquery for the same evaluation-order reason as the gap query.
Follow-up
- Relay failover redelivers events. Does a duplicate break the gap query, and how would you detect one from this table alone?
- Turn the gap check into a continuous monitor rather than a query someone runs after an incident. What does it watch?
How do you ensure the scalability of a backend system?
How do you ensure the scalability of a backend system?
Approach
- Fix the scope first: who calls this, how often, and what they do when it fails.
- Name the read and write paths separately; they rarely have the same bottleneck.
- Choose a partition key and say what query it makes expensive.
- State the consistency you need, and where you are willing to be stale.
Follow-up
- What breaks first when traffic grows ten times?
- How does this behave when that dependency is down for an hour?
Describe a challenging technical problem you faced and how you resolved it.
Describe a challenging technical problem you faced and how you resolved it.
Approach
- Clarify what is being asked and what a complete answer contains.
- State your assumptions explicitly before working the problem.
- Say what you would check first and why it is the highest-information step.
- Work from the requirement backwards to the design.
Follow-up
- What assumption would you test first?
- How would you know your answer was wrong?
If given a performance issue in a service, what steps would you take to diagnose and fix it?
If given a performance issue in a service, what steps would you take to diagnose and fix it?
Approach
- Clarify what is being asked and what a complete answer contains.
- State your assumptions explicitly before working the problem.
- Say what you would check first and why it is the highest-information step.
- Work from the requirement backwards to the design.
Follow-up
- What assumption would you test first?
- How would you know your answer was wrong?
Describe how you would prioritize features for a product in a tight deadline scenario.
Describe how you would prioritize features for a product in a tight deadline scenario.
Approach
- Clarify what is being asked and what a complete answer contains.
- State your assumptions explicitly before working the problem.
- Say what you would check first and why it is the highest-information step.
- Work from the requirement backwards to the design.
Follow-up
- What assumption would you test first?
- How would you know your answer was wrong?
What tools and methodologies do you use for debugging and testing your code?
What tools and methodologies do you use for debugging and testing your code?
Approach
- Establish what changed and when, before forming any theory.
- Pick a bisection that eliminates candidates whichever way it turns out.
- Check the instrumentation before believing the symptom.
- Separate the trigger from the cause; the deploy is rarely the bug.
Follow-up
- What would you look at first, and what would it rule out?
- How would you tell a cause from a coincidence here?
Built from the rounds and topics Censys candidates report.
Prepare, practise & reflect
One practical outcome each day. Spend longer where you need it.
0 / 7 done01Map the Censys loop
- Write out the reported sequence: Initial Screening, Technical Assessments, Interviews with Team Members.
- For each round, write one sentence on what it is judging, from the description above, and mark the one you are least ready for.
Deliverable: A one-page map of the 3 reported rounds, with the weakest marked.
02Work Kubernetes (K8s)
- Spend the session on Kubernetes (K8s), which Censys candidates report being tested on.
- Write one worked example in Kubernetes (K8s) and time yourself on it.
Deliverable: One timed worked example in Kubernetes (K8s).
03Work API Development
- Spend the session on API Development, which Censys candidates report being tested on.
- Write one worked example in API Development and time yourself on it.
Deliverable: One timed worked example in API Development.
04Work Coding Assessments (Take-home/Timed)
- Spend the session on Coding Assessments (Take-home/Timed), which Censys candidates report being tested on.
- Write one worked example in Coding Assessments (Take-home/Timed) and time yourself on it.
Deliverable: One timed worked example in Coding Assessments (Take-home/Timed).
05Answer out loud: Technical / Domain Questions
- Answer aloud, timed: What is your experience with cloud services and their implementation?
- Answer aloud, timed: How do you ensure the scalability of a backend system?
Deliverable: Spoken answers to 2 reported Technical / Domain Questions question(s), under time.
06Answer out loud: Problem-Solving / Case Studies
- Answer aloud, timed: How would you approach designing a system to handle millions of concurrent users?
- Answer aloud, timed: If given a performance issue in a service, what steps would you take to diagnose and fix it?
Deliverable: Spoken answers to 2 reported Problem-Solving / Case Studies question(s), under time.
07Answer out loud: Behavioral / Leadership
- Answer aloud, timed: Can you describe a time when you had to work collaboratively with a team to achieve a goal?
- Answer aloud, timed: How do you handle conflicts within a team?
Deliverable: Spoken answers to 2 reported Behavioral / Leadership question(s), under time.
Expand any day for tasks and deliverables. Your progress is saved on this device.
Behavioural rounds judge the decision you made and what it cost.
What is your experience with cloud services and their implementation?
What is your experience with cloud services and their implementation?
Approach
- Pick a story where you made the decision, not one where you watched it.
- State the situation in two sentences and spend the rest on the reasoning.
- Give the blast radius: what could have broken, and what you measured.
- Name the disagreement and how you resolved it with evidence.
Follow-up
- What would you do differently if you ran that again?
- How did you know your change caused the improvement?
Can you describe a time when you had to work collaboratively with a team to achieve a goal?
Can you describe a time when you had to work collaboratively with a team to achieve a goal?
Approach
- Pick a story where you made the decision, not one where you watched it.
- State the situation in two sentences and spend the rest on the reasoning.
- Give the blast radius: what could have broken, and what you measured.
- Name the disagreement and how you resolved it with evidence.
Follow-up
- What would you do differently if you ran that again?
- How did you know your change caused the improvement?
How do you handle conflicts within a team?
How do you handle conflicts within a team?
Approach
- Pick a story where you made the decision, not one where you watched it.
- State the situation in two sentences and spend the rest on the reasoning.
- Give the blast radius: what could have broken, and what you measured.
- Name the disagreement and how you resolved it with evidence.
Follow-up
- What would you do differently if you ran that again?
- How did you know your change caused the improvement?
What motivates you to deliver high-quality work?
What motivates you to deliver high-quality work?
Approach
- Pick a story where you made the decision, not one where you watched it.
- State the situation in two sentences and spend the rest on the reasoning.
- Give the blast radius: what could have broken, and what you measured.
- Name the disagreement and how you resolved it with evidence.
Follow-up
- What would you do differently if you ran that again?
- How did you know your change caused the improvement?
- 01
What is your experience with cloud services and their implementation?
- 02
Can you describe a time when you had to work collaboratively with a team to achieve a goal?
- 03
How do you handle conflicts within a team?
- 04
What motivates you to deliver high-quality work?
How difficult are the interviews, and how much preparation time is typical?
The interviews at Censys are designed to be challenging but fair. Candidates typically spend 2-4 weeks preparing, focusing on technical skills, problem-solving, and cultural fit.
Censys Software Engineer candidate reports ↗What differentiates successful candidates?
Successful candidates often demonstrate a strong alignment with Censys' values, have excellent communication skills, and possess a solid technical foundation with the ability to solve complex problems.
Censys Software Engineer candidate reports ↗What is the company culture like?
The culture at Censys emphasizes collaboration, transparency, and a commitment to continuous improvement. You will find a supportive environment that encourages innovation and initiative.
Censys Software Engineer candidate reports ↗What is the typical timeline from initial screen to offer?
The timeline can vary, but candidates can generally expect a decision within 4-6 weeks from their initial interview, depending on the number of interview rounds and team availability.
Censys Software Engineer candidate reports ↗Are remote work opportunities available?
Yes, many positions, including the Software Engineer role, offer remote work options, allowing for flexibility in your work environment.
Censys Software Engineer candidate reports ↗What topics does Censys test in interviews?
Censys interviews most often cover Distributed Systems, Backend Engineering, Core Services Architecture, Kubernetes (K8s), and Business Analysis. The exact emphasis depends on the specific role you apply for.
Censys Software Engineer candidate reports ↗Sources & methodology 3 sources ↗
Official role evidence, timestamped platform data and clearly labeled preparation advice.
- 01Censys Software Engineer candidate reports ↗
Company-reported rounds, questions and FAQ.
candidate · Accessed 2026-09-22 - 02PracHub Software Engineer practice ↗
PracHub practice material, not company-reported.
platform · Accessed 2026-09-22 - 03PracHub preparation framework ↗
PracHub preparation guidance.
platform · Accessed 2026-09-22
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