Tink Software Engineer Interview Guide

The 60-second brief

As a Software Engineer at Tink, you are at the absolute center of Europe's leading open banking platform. Tink enables banks, fintechs, and startups to build the future of financial services by providing a single, robust API to access aggregated financial data, initiate payments, and enrich transactions. In this role, your primary responsibility is to design, build, and maintain the highly scalable, secure, and resilient infrastructure that connects thousands of banks and millions of active consumers. The engineering organization at Tink operates at a massive scale, processing millions of API calls daily with extreme reliability and low latency. As a Software Engineer, you will work on complex distributed systems, deal with intricate bank integration challenges, and ensure the highest standards of data security and privacy.

This guide is scoped to a Software Engineer candidate at Tink.

Focus areas

• Java
• SQL
• API Integration

The Tink interview process

Tink candidates report 5 rounds over 4-6 weeks. The stages below are what candidates describe, not a published process.

Recruiter Screening

Initial discussion about your background, interests, and alignment with Tink's culture.

What to demonstrate

• Initial discussion about your background, interests, and alignment with Tink's culture
• Depth in Java

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 Assessment

Involves an online coding challenge or a practical API integration home task.

What to demonstrate

• Involves an online coding challenge or a practical API integration home task
• Depth in Java

How to prepare

• Answer aloud and timed: How would you structure a clean, maintainable solution to process a stream of financial events?
• Answer aloud and timed: Write a function to detect anomalies in user transaction histories.

Technical Interviews

Deep-dive interviews focusing on technical skills and system design.

What to demonstrate

• Deep-dive interviews focusing on technical skills and system design
• Depth in Java

How to prepare

• Answer aloud and timed: Explain how garbage collection works in Java and how you would diagnose a memory leak in a production environment.
• Answer aloud and timed: How do you manage database concurrency and prevent race conditions when updating account balances?

Hiring Manager Interview

Final interview with the hiring manager to assess fit and expectations.

What to demonstrate

• Final interview with the hiring manager to assess fit and expectations
• Depth in Java

How to prepare

• Prepare two projects you led end to end, each with the decision you owned and what it cost.
• Have three questions about the team's roadmap and how success is measured in the first six months.

Vibe Check

Casual discussion with potential future team members to gauge team dynamics.

What to demonstrate

• Casual discussion with potential future team members to gauge team dynamics
• Depth in Java

How to prepare

• Answer aloud and timed: Explain the contract between equals and hashCode in Java and why it is critical for collection classes.
• Answer aloud and timed: Design a highly available API gateway that can handle rate limiting and token validation for millions of requests.

Where candidates lose points

Communicate your thoughts clearly

During coding and system design interviews, talk through your reasoning. Explain the trade-offs of different approaches and why you are choosing a specific solution.

Focus on clean code

Tink engineers value code readability and maintainability. Avoid overly clever one-liners; instead, write clean, well-structured, and self-documenting code.

Ask clarifying questions

If a problem statement is ambiguous, do not hesitate to ask your interviewer for guidance. They appreciate candidates who clarify requirements before diving into implementation.

Questions & practice

Write a program to solve a classic logical optimization problem under time and memory constraints.

Medium · Coding & Problem Solving

Approach

1. Say what the runtime actually does before reasoning about the code.
2. Name what is shared across threads and what owns each piece of state.
3. Identify the window where an invariant is briefly untrue.
4. 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?

Implement a robust parser for a custom transaction data format.

Medium · Coding & Problem Solving

Approach

1. Restate the input: its shape, its size, and what is guaranteed about it.
2. Name the brute-force solution and its complexity before improving on it.
3. Choose the data structure from the access pattern, not from familiarity.
4. 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 clean, maintainable solution to process a stream of financial events?

Medium · Coding & Problem Solving

Approach

1. Restate the input: its shape, its size, and what is guaranteed about it.
2. Name the brute-force solution and its complexity before improving on it.
3. Choose the data structure from the access pattern, not from familiarity.
4. 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?

Write a function to detect anomalies in user transaction histories.

Medium · Coding & Problem Solving

Approach

1. Restate the input: its shape, its size, and what is guaranteed about it.
2. Name the brute-force solution and its complexity before improving on it.
3. Choose the data structure from the access pattern, not from familiarity.
4. 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?

Explain how garbage collection works in Java and how you would diagnose a memory leak in a production environm

Medium · Technical & Language-Specific (Java & Da

Explain how garbage collection works in Java and how you would diagnose a memory leak in a production environment.

Approach

1. Say what the runtime actually does before reasoning about the code.
2. Name what is shared across threads and what owns each piece of state.
3. Identify the window where an invariant is briefly untrue.
4. 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?

How do you manage database concurrency and prevent race conditions when updating account balances?

Medium · Technical & Language-Specific (Java & Da

Approach

1. Say what the runtime actually does before reasoning about the code.
2. Name what is shared across threads and what owns each piece of state.
3. Identify the window where an invariant is briefly untrue.
4. 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?

What are the differences between optimistic and pessimistic locking, and when would you use each?

Medium · Technical & Language-Specific (Java & Da

Approach

1. Say what the runtime actually does before reasoning about the code.
2. Name what is shared across threads and what owns each piece of state.
3. Identify the window where an invariant is briefly untrue.
4. 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?

Explain the contract between equals and hashCode in Java and why it is critical for collection classes.

Medium · Technical & Language-Specific (Java & Da

Approach

1. Say what the runtime actually does before reasoning about the code.
2. Name what is shared across threads and what owns each piece of state.
3. Identify the window where an invariant is briefly untrue.
4. 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 and optimize a complex SQL query to retrieve aggregated transaction data across multiple tables.

Medium · Technical & Language-Specific (Java & Da

Approach

1. Name the grain you start from and join outward from it.
2. Check whether any join is one-to-many before aggregating, or the sums inflate.
3. Say which index the query would use, and what makes it unusable.
4. 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?

Replace offset paging on the resource feed with keyset

Easy · keyset pagination · composite index · sort order

resource holds resource_id, tenant_id, owner_user_id, title, body_ref, version, status ('draft','active','archived','deleted'), created_at, updated_at, deleted_at, with an index on (tenant_id, status, updated_at DESC, resource_id DESC). The listing endpoint returns active resources for one tenant, newest update first, 50 per page, today with LIMIT 50 OFFSET n. Tenants reach page 400 and rows are created while they read. Write the keyset query, define what the cursor carries and how it is encoded, and say which part of the index each predicate uses. Assume PostgreSQL 16.

Approach

1. Name the two failures separately. OFFSET 20000 makes the server produce and discard 20,000 rows, so page cost grows with depth rather than with page size. Independently, any write that changes how many rows sort above the offset moves the window between two fetches, and the direction decides which anomaly you get: an insert lands at the head of updated_at DESC and pushes already-returned rows down past the boundary, so they are returned a second time; a delete above the offset, or a row whose updated_at is bumped above the cursor, pulls rows up and one is never returned at all. Nothing in the response reveals either.
2. Write the seek: WHERE tenant_id = $1 AND status = 'active' AND (updated_at, resource_id) < ($2, $3) ORDER BY updated_at DESC, resource_id DESC LIMIT 50. The row-value comparison is one index range rather than a disjunction, and both columns are NOT NULL, which is what makes that comparison well defined.
3. Map each predicate onto the index: tenant_id and status are equality on the leading columns, (updated_at, resource_id) is the range, and the ORDER BY matches the index order so no Sort node appears and the scan stops after 50 rows. The DESC in the definition only matters for mixed directions — a plain ascending btree on the same columns is read backwards for this query.
4. Put both sort columns in the cursor and nothing the client can tamper with into another tenant: base64 of (updated_at, resource_id), validated server-side, with tenant_id taken from the principal.

Follow-up

• The client asks for 'jump to page 400'. What do you offer instead, and what does the honest version cost?
• Sort order becomes user-selectable across four columns. How many indexes is that, and which would you refuse to add?

Design a highly available API gateway that can handle rate limiting and token validation for millions of reque

Medium · System Design & API Integration

Design a highly available API gateway that can handle rate limiting and token validation for millions of requests.

Approach

1. Say who the caller is and what they do when the call fails halfway.
2. Define the identity of a request so a retry cannot double-apply it.
3. Separate accepted, pending, failed and confirmed; they are different facts.
4. Design the error taxonomy before the success shape; callers branch on it.

Follow-up

• What happens if the caller retries after a timeout?
• How does a client discover it is on an old version of this contract?

How would you design a system to integrate with multiple external bank APIs, keeping in mind that some may be

Medium · System Design & API Integration

How would you design a system to integrate with multiple external bank APIs, keeping in mind that some may be slow or unreliable?

Approach

1. Fix the scope first: who calls this, how often, and what they do when it fails.
2. Name the read and write paths separately; they rarely have the same bottleneck.
3. Choose a partition key and say what query it makes expensive.
4. 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?

Design a distributed transaction processing system that guarantees exactly-once processing.

Medium · System Design & API Integration

Approach

1. Fix the scope first: who calls this, how often, and what they do when it fails.
2. Name the read and write paths separately; they rarely have the same bottleneck.
3. Choose a partition key and say what query it makes expensive.
4. 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?

One log partition stops advancing while the others drain

Easy · poison message · head-of-line blocking · consumer lag

Search results for a subset of tenants are hours stale; the rest are current. The projection consumer reports lag of zero on 15 of 16 partitions and 400,000 on one. Its error rate is flat and its CPU is idle. outbox_event has no pending rows older than a second, so the relay has published everything it holds. Identify the mechanism, give the ordered checks, and state what you do in the first ten minutes versus what you change permanently.

Approach

1. Read the lag distribution first. A slow consumer lags everywhere; zero on fifteen partitions and 400,000 on one is not throughput. Idle CPU on the stuck partition means the consumer is not advancing its offset at all, which points at one message it cannot get past rather than at a rate problem.
2. Exonerate the producer before touching the consumer. No pending outbox rows older than a second means the relay published, so the event exists in the log. This separates never sent from sent and never applied, which are different code paths and usually different owners.
3. Read the message at the stuck offset and the handler's log lines for its event_id. A flat error rate with no progress has two explanations and you must distinguish them: the handler is throwing and the retry loop is swallowing it, or the handler is blocking on something and never returning. Idle CPU with no error lines favours the second.
4. Mitigate before diagnosing further. Move the offending event to a dead-letter store and commit the offset past it. Adding consumers does nothing here, because a partition is consumed by exactly one member of the group, and the blast radius is every aggregate hashed to that partition, not only the aggregate that produced the bad event.

Follow-up

• The dead-lettered event carried aggregate_version 7 and the projection had applied 6. What must the replay do differently if 8 and 9 landed in the meantime?
• How do you show staleness to the user while the partition is behind, given the API already returns the projection's watermark?

Suggested practice checklist

Built from the rounds and topics Tink candidates report.

Day 1 — Map the Tink loop

• Write out the reported sequence: Recruiter Screening, Technical Assessment, Technical Interviews, Hiring Manager Interview, Vibe Check.
• 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 5 reported rounds, with the weakest marked.

Day 2 — Work Java

• Spend the session on Java, which Tink candidates report being tested on.
• Write one worked example in Java and time yourself on it.

Deliverable: One timed worked example in Java.

Day 3 — Work SQL

• Spend the session on SQL, which Tink candidates report being tested on.
• Write one worked example in SQL and time yourself on it.

Deliverable: One timed worked example in SQL.

Day 4 — Work API Integration

• Spend the session on API Integration, which Tink candidates report being tested on.
• Write one worked example in API Integration and time yourself on it.

Deliverable: One timed worked example in API Integration.

Day 5 — Answer out loud: Coding & Problem Solving

• Answer aloud, timed: Write a program to solve a classic logical optimization problem under time and memory constraints.
• Answer aloud, timed: Implement a robust parser for a custom transaction data format.

Deliverable: Spoken answers to 2 reported Coding & Problem Solving question(s), under time.

Day 6 — Answer out loud: Technical & Language-Specific (Java & Databases)

• Answer aloud, timed: Explain how garbage collection works in Java and how you would diagnose a memory leak in a production environment.
• Answer aloud, timed: How do you manage database concurrency and prevent race conditions when updating account balances?

Deliverable: Spoken answers to 2 reported Technical & Language-Specific (Java & Databases) question(s), under time.

Day 7 — Answer out loud: System Design & API Integration

• Answer aloud, timed: Design a highly available API gateway that can handle rate limiting and token validation for millions of requests.
• Answer aloud, timed: How would you design a system to integrate with multiple external bank APIs, keeping in mind that some may be slow or unreliable?

Deliverable: Spoken answers to 2 reported System Design & API Integration question(s), under time.

Behavioural preparation

Behavioural rounds judge the decision you made and what it cost.

How do you handle schema migrations in a large-scale database with zero downtime?

Medium · System Design & API Integration

Approach

1. Pick a story where you made the decision, not one where you watched it.
2. State the situation in two sentences and spend the rest on the reasoning.
3. Give the blast radius: what could have broken, and what you measured.
4. 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 time when you had to make a technical trade-off under a tight deadline. What was the outcome?

Medium · Behavioral & Culture Fit

Approach

1. Pick a story where you made the decision, not one where you watched it.
2. State the situation in two sentences and spend the rest on the reasoning.
3. Give the blast radius: what could have broken, and what you measured.
4. 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 a situation where a team member strongly disagrees with your architectural proposal?

Medium · Behavioral & Culture Fit

Approach

1. Pick a story where you made the decision, not one where you watched it.
2. State the situation in two sentences and spend the rest on the reasoning.
3. Give the blast radius: what could have broken, and what you measured.
4. 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 me about a complex technical problem you solved recently. How did you explain it to non-technical stakeho

Medium · Behavioral & Culture Fit

Tell me about a complex technical problem you solved recently. How did you explain it to non-technical stakeholders?

Approach

1. Pick a story where you made the decision, not one where you watched it.
2. State the situation in two sentences and spend the rest on the reasoning.
3. Give the blast radius: what could have broken, and what you measured.
4. 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 work in the fintech space, and how do you keep up with industry trends?

Medium · Behavioral & Culture Fit

Approach

1. Pick a story where you made the decision, not one where you watched it.
2. State the situation in two sentences and spend the rest on the reasoning.
3. Give the blast radius: what could have broken, and what you measured.
4. 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?