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Adyen

Large Enterprises

Adyen is a Dutch payment company that provides a global financial technology platform enabling businesses to accept payments online, in-app, and in-store. It is known for its single unified platform serving large enterprises and multinational merchants worldwide.

3 interview notes · updated Jul 2026

Adyen·Software Engineer·Technical Phone Screen

Jun 2026
Interviewed for a software engineering role at Adyen and got two fairly meaty technical problems back to back. One was a classic cache design question, the other a combinatorics/backtracking problem. Both had meaningful follow-ups that pushed past the obvious answers.
  • Design and implement an in-memory LRU cache that supports get and put operations in O(1) time.
  • Given a list of candidate numbers and a target, find all unique combinations that sum to the target, where each candidate can be used any number of times.

“I knew the doubly linked list plus hash map combo going in, but fumbled a bit explaining why sentinel dummy nodes matter.”

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Adyen·Software Engineer·Onsite - System Design / Architecture

May 2026
System design round at Adyen for a software engineer role, two big back-to-back design problems with a lot of depth expected on both. The bar felt high and the questions were very production-focused, not the usual whiteboard-y stuff.
  • Design a production-ready thread-safe LRU caching service, covering API design, concurrency control, eviction correctness, TTL and size limits, metrics, and observability.
  • How would you scale that LRU cache across multiple instances, handling hot keys, replication and failover, backpressure, and data consistency?
  • Design a compute-heavy API for finding transfer combinations that needs to handle request spikes, covering stateless vs stateful worker design, per-request memory management, caching and precomputation, request deduplication, rate limiting, timeouts, and idempotency.
  • Walk through your capacity estimates and testing plan for the transfer combinations API under spike traffic.

“Started with the basics of a doubly linked list plus hashmap, but they pushed hard on concurrency almost immediately.”

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Adyen·Software Engineer·Onsite - System Design / Architecture

May 2026
Adyen software engineer interview focused heavily on a deep technical walkthrough of a past project. Not a casual chat, they really wanted to get into the weeds on what you personally built versus what your team did.
  • Walk me through a complex project you worked on recently. Start with the high-level architecture, then go deep on your specific contributions: what you designed, what decisions you owned, what the trade-offs were, any measurable performance or reliability wins, how you worked with other teams, and the hardest problem you personally had to solve. Be clear about what was yours versus what others did, and what you'd change if you did it again.

“This is basically the whole interview in one question.”

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