As a Software Engineer at Dun & Bradstreet, you are at the intersection of massive-scale data processing and high-stakes business intelligence. You will be tasked with building, maintaining, and scaling the infrastructure that powers global commercial data, helping the world's most influential companies make informed credit, supply chain, and marketing decisions. Your work directly impacts the reliability and accuracy of the Dun & Bradstreet Data Cloud, a platform that serves as the backbone for millions of business decisions every day. This role is both technically demanding and strategically significant. You won’t just be writing code; you will be architecting solutions that handle complex data integration, cloud-native services, and high-performance engineering challenges. Whether you are working on modernizing legacy systems or building new features for the Power Platform or Microsoft Fabric integrations, you are expected to operate with high ownership, architectural rigor, and a focus on delivering robust, maintainable software.
Recruiter Call
reportedInitial screening call with a recruiter to gauge your background and interest.
What to demonstrate
- Initial screening call with a recruiter to gauge your background and interest
- Depth in Core Java (OOP fundamentals)
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
reportedSeries of technical assessments including online coding tests, whiteboard design sessions, or pair programming.
What to demonstrate
- Series of technical assessments including online coding tests, whiteboard design sessions, or pair programming
- Depth in Core Java (OOP fundamentals)
How to prepare
- Answer aloud and timed: What are the differences between REST and SOAP architectures?
- Answer aloud and timed: How do you implement Lazy Loading in one-to-many mappings?
Behavioral Interviews
reportedInterviews with engineering managers and team leads to evaluate team dynamics and individual contributions.
What to demonstrate
- Interviews with engineering managers and team leads to evaluate team dynamics and individual contributions
- Depth in Core Java (OOP fundamentals)
How to prepare
- Prepare three examples from your own work, each with a decision you made and an outcome you can quantify.
- Re-read the description of the behavioral interviews above and write down what you would ask to confirm before it.
PracHub editorial advice for the preparation topics above.
Own your answers
If you don’t know an answer, don't bluff. Explain how you would go about finding the answer or solving the problem.
Focus on communication
During pair programming, explain your thought process out loud. The interviewer is as interested in how you think as they are in the final code.
Prepare for behavioral questions
Use the STAR (Situation, Task, Action, Result) method to structure your answers to behavioral prompts.
Research the company
Be ready to discuss what Dun & Bradstreet does and why you are interested in the specific data-driven problems they solve.
Choose a category, try a prompt, then open its approach, worked solution or follow-up when you need it.
Explain the internal workings of a ConcurrentHashMap in Java.
Explain the internal workings of a ConcurrentHashMap in Java.
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 string in Java.
Write a function to reverse a string in Java.
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?
Solve a binary search-related problem using CodePad.
Solve a binary search-related problem using CodePad.
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?
Implement a DFS (Depth-First Search) algorithm.
Implement a DFS (Depth-First Search) algorithm.
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 structure a SQL query to optimize performance for a large dataset?
How would you structure a SQL query to optimize performance for a large dataset?
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?
Explain why the owner filter ignores the listing index
The only index on resource is (tenant_id, status, updated_at DESC, resource_id DESC). A new endpoint returns one user's resources across all statuses, newest created first: WHERE tenant_id = $1 AND owner_user_id = $2 ORDER BY created_at DESC LIMIT 20. On a tenant with 2M rows it takes 900 ms and EXPLAIN shows a sort above a large scan. Explain precisely why the existing index cannot serve it, give the index that can, and state which of these the new index still will not help: owner_user_id alone across tenants; the same query ordered by updated_at. PostgreSQL 16.
Approach
- Separate the two jobs an index does. For filtering, a composite btree is seekable only on a left prefix, so with no predicate on status the scan can at best range over tenant_id and test owner_user_id per row; PostgreSQL 16 has no btree skip scan to jump the unconstrained column.
- For ordering, the index is sorted by (status, updated_at) within a tenant and not by created_at, so the LIMIT cannot stop early: every matching row is read and then sorted. That is the 'Sort Method: top-N heapsort' line, and it is why the plan reads 2M rows to answer with 20.
- Derive the replacement from the access path — equality, equality, then the ordering column: CREATE INDEX CONCURRENTLY ON resource (tenant_id, owner_user_id, created_at DESC). The scan seeks to the (tenant, owner) range and walks 20 entries in order, so the Sort node disappears along with the row-read.
- Treat INCLUDE (title, status) as conditional, not free. An index-only scan still visits the heap for any row whose page is not marked all-visible, so on a table taking 1.2k writes/second the win depends on autovacuum keeping the visibility map current, and the wider index costs more on every insert.
Follow-up
- 90% of rows are status='active'. Would a partial index WHERE status = 'active' change your answer, and for which of the three queries?
- A dashboard runs this for 40 owners in one page load. What changes about the design?
What are the differences between REST and SOAP architectures?
What are the differences between REST and SOAP architectures?
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?
How do you implement Lazy Loading in one-to-many mappings?
How do you implement Lazy Loading in one-to-many mappings?
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 the core principles of S.O.L.I.D. and how you apply them to your code.
Describe the core principles of S.O.L.I.D. and how you apply them to your code.
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?
Design a high-level system for an e-commerce clone (e.g., Amazon).
Design a high-level system for an e-commerce clone (e.g., Amazon).
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?
Every query on one table stalls for forty seconds mid-deploy
During a release on PostgreSQL, every query touching resource times out for about 40 seconds and then recovers with no intervention. The release ran one migration, ALTER TABLE resource ADD COLUMN archived_reason TEXT, and the migration log shows it completing in 6 ms. Unrelated tables showed no change in error rate. Explain how a 6 ms statement caused a 40-second stall, give the ordered checks you would run on a live system to confirm it, and give the migration procedure that prevents a repeat.
Approach
- Separate the statement's duration from the lock's duration. ADD COLUMN with no default is a catalogue-only change and genuinely runs in milliseconds, but it requires ACCESS EXCLUSIVE, and it cannot acquire that until every transaction already touching the table has finished.
- Account for the queueing, which is the part that surprises people. A lock request that is waiting blocks later requests for conflicting modes behind it rather than letting them overtake, so one long-open transaction holds the DDL and the DDL holds all the traffic. The stall length is set by the longest open transaction, not by the size of the change.
- Confirm on a live system in this order: pg_stat_activity for that table ordered by xact_start, looking for the oldest transaction and specifically for state = idle in transaction; then pg_locks where granted = false to find the waiter; then join them on pid to name blocker and blocked. pg_blocking_pids() does that join for you and is the fastest single call.
- Prevent rather than merely time it better. Set lock_timeout to a second or two on the migration session so the DDL abandons the queue after a bounded wait and is retried, instead of holding it for as long as the oldest transaction lives. Be exact about what that buys: queries arriving during the wait still queue behind the pending ACCESS EXCLUSIVE request, so each attempt costs them up to one lock_timeout of added latency. The outage goes from 40 seconds to about one second per attempt, not to zero. Also run migrations away from deploy-time peaks, and put a statement timeout and an idle-in-transaction timeout on the analytics role that opens the long transactions.
Follow-up
- The same release also wants NOT NULL on that column. What is the sequence that gets there without a long lock?
- Your lock_timeout retry fails ten times in a row because the analytics transaction is always open. What do you change?
Built from the rounds and topics Dun & Bradstreet candidates report.
Prepare, practise & reflect
One practical outcome each day. Spend longer where you need it.
0 / 7 done01Map the Dun & Bradstreet loop
- Write out the reported sequence: Recruiter Call, Technical Assessments, Behavioral Interviews.
- 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 Core Java (OOP fundamentals)
- Spend the session on Core Java (OOP fundamentals), which Dun & Bradstreet candidates report being tested on.
- Write one worked example in Core Java (OOP fundamentals) and time yourself on it.
Deliverable: One timed worked example in Core Java (OOP fundamentals).
03Work Hibernate (ORM)
- Spend the session on Hibernate (ORM), which Dun & Bradstreet candidates report being tested on.
- Write one worked example in Hibernate (ORM) and time yourself on it.
Deliverable: One timed worked example in Hibernate (ORM).
04Work Spring MVC
- Spend the session on Spring MVC, which Dun & Bradstreet candidates report being tested on.
- Write one worked example in Spring MVC and time yourself on it.
Deliverable: One timed worked example in Spring MVC.
05Answer out loud: Technical & Domain Expertise
- Answer aloud, timed: Explain the internal workings of a ConcurrentHashMap in Java.
- Answer aloud, timed: How do you handle the N+1 problem when using Hibernate?
Deliverable: Spoken answers to 2 reported Technical & Domain Expertise question(s), under time.
06Answer out loud: Coding & Problem Solving
- Answer aloud, timed: Write a function to reverse a string in Java.
- Answer aloud, timed: Solve a binary search-related problem using CodePad.
Deliverable: Spoken answers to 2 reported Coding & Problem Solving question(s), under time.
07Answer out loud: Behavioral & Situational
- Answer aloud, timed: Tell us about a time you had to resolve a conflict within your engineering team.
- Answer aloud, timed: How do you approach learning a new technology stack on the fly?
Deliverable: Spoken answers to 2 reported Behavioral & Situational 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.
How do you handle the N+1 problem when using Hibernate?
How do you handle the N+1 problem when using Hibernate?
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?
Tell us about a time you had to resolve a conflict within your engineering team.
Tell us about a time you had to resolve a conflict within your engineering 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?
How do you approach learning a new technology stack on the fly?
How do you approach learning a new technology stack on the fly?
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?
Describe a project where you had to balance technical debt with feature delivery.
Describe a project where you had to balance technical debt with feature delivery.
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 communicate complex technical tradeoffs to non-technical stakeholders?
How do you communicate complex technical tradeoffs to non-technical stakeholders?
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
How do you handle the N+1 problem when using Hibernate?
- 02
Tell us about a time you had to resolve a conflict within your engineering team.
- 03
How do you approach learning a new technology stack on the fly?
- 04
Describe a project where you had to balance technical debt with feature delivery.
How difficult are the technical interviews?
The difficulty is moderate to high, depending on the seniority of the role. You will be expected to demonstrate proficiency in your core language and solve algorithmic problems, but the emphasis is often on practical, real-world engineering rather than obscure trivia.
Dun & Bradstreet Software Engineer candidate reports ↗What is the company culture like?
Dun & Bradstreet fosters a professional, collaborative environment. While some candidates have reported varied experiences with communication, the core engineering teams are generally described as polite, technical, and focused on building robust products.
Dun & Bradstreet Software Engineer candidate reports ↗How long does the process take?
The process can take anywhere from a few weeks to over a month. It is important to maintain proactive communication with your recruiter to stay informed on your status.
Dun & Bradstreet Software Engineer candidate reports ↗What topics does Dun & Bradstreet test in interviews?
Dun & Bradstreet interviews most often cover SQL, Stakeholder Management, Behavioral Interviewing, Requirements Gathering, and Python. The exact emphasis depends on the specific role you apply for.
Dun & Bradstreet Software Engineer candidate reports ↗Sources & methodology 3 sources ↗
No official company page is cited. Rounds and questions come from candidate reports and PracHub editorial material; each source shows the date it was read.
- 01Dun & Bradstreet Software Engineer candidate reports ↗
Company-reported rounds, questions and FAQ.
Candidate reports · Accessed 2026-09-22 - 02PracHub Software Engineer practice ↗
PracHub practice material, not company-reported.
PracHub page · Accessed 2026-09-22 - 03PracHub preparation framework ↗
PracHub preparation guidance.
PracHub page · Accessed 2026-09-22
Explore related engineering environments and compare the preparation focus.
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