Top 8 Backend Development Interview Questions
Backend engineering interview questions for European tech roles. API design, database optimization, microservices, and system design — essential for roles at SAP, Adyen, and Klarna.
Design a RESTful API for a multi-tenant SaaS application.
Expert Tip: Tenant isolation, auth, rate limiting, versioning. Discuss OpenAPI spec.
Explain the differences between SQL and NoSQL databases. When would you choose each?
Expert Tip: ACID vs BASE, schema rigidity, scale patterns. European fintech loves PostgreSQL.
How would you implement distributed transactions across microservices?
Expert Tip: Saga pattern (orchestration vs choreography), eventual consistency, compensation.
Design a caching strategy for a high-traffic European e-commerce site.
Expert Tip: CDN (Cloudflare), Redis, cache invalidation, stale-while-revalidate.
Explain OAuth 2.0 and OpenID Connect.
Expert Tip: Authorization vs authentication. Grant types, tokens, scopes.
How would you handle database migrations in a zero-downtime deployment?
Expert Tip: Expand-contract pattern, backwards-compatible changes, feature flags.
What is GraphQL? When would you prefer it over REST?
Expert Tip: Over-fetching, under-fetching solutions. Discuss N+1 problem and DataLoader.
Design an event-driven architecture for processing 10M daily job notifications.
Expert Tip: Kafka/SQS, consumer groups, dead letter queues, idempotency, monitoring.
Recommended Resources
Designing Data-Intensive Applications
Martin Kleppmann's essential guide to distributed systems.
PostgreSQL documentation
Most popular database in European tech — know it deeply.
System Design Primer (GitHub)
Free, comprehensive system design study guide.