Trade Republic Senior Engineer

The company, its products, tech stack, engineering principles, and regulatory frame: the lens every other round is graded through.

1. 1 Trade Republic: Products, Business Model, and the Engineer's Role advanced The product suite, how the company earns, and what a senior engineer owns across brokerage, neobank, bonds, and cards.
2. 2 The Trade Republic Interview Loop Decoded intermediate The five rounds, what each grades, and the documented failure modes that sink candidates.
3. 3 Trade Republic's Tech Stack and Tech Radar advanced Kotlin, Postgres, Kafka, Redis, Elasticsearch, Kubernetes, AWS, and the Tech Radar plus RFC process that governs choice.
4. 4 Engineering Principles in Practice advanced Autonomy and alignment, hexagonal architecture, documentation as routine, and RFC-driven decisions that show cultural fit.
5. 5 The Regulatory Frame for a Fintech Engineer advanced BaFin, MiFID II, KYC and AML, and client-asset segregation that constrain every design decision.

The brokerage domain a Trade Republic engineer builds for: order lifecycle, matching, market data, ledgers, and money safety.

1. 6 The Order Lifecycle in a Brokerage expert From tap-to-trade through routing, execution, clearing, settlement, and custody, with price-time priority.
2. 7 Order Matching Engine Internals expert Limit-order book structure, price-time matching, and the correctness guarantees a high-frequency engine must defend.
3. 8 Market Data Ingestion and Normalization expert Why assuming consistent exchange formats is a trap, and how FIX and normalized quote pipelines are built.
4. 9 Cash, Balances, and Double-Entry Ledgering expert Idempotent deposits and withdrawals, double-entry ledgers, and the balance-update plus outbox consistency problem.
5. 10 Idempotency, Exactly-Once, and Money Safety expert Why financial correctness is not at-least-once: dedup, sequence numbers, and poison pills in money movement.

The consistency and reliability machinery the platform is built on: the outbox pattern, change data capture, transactions, partitioning, and concurrency.

1. 11 The Outbox Pattern, Deeply expert All six outbox incidents, the partitioned-outbox revamp, and why this is Trade Republic's flagship reliability pattern.
2. 12 Change Data Capture and Event Reliability expert WAL logical replication, Debezium, Avro and Schema Registry, and the dual-write problem CDC solves.
3. 13 Consistency, Transactions, and Rollbacks expert Two-phase commit versus saga versus outbox, isolation levels, and what handling rollback actually means for money.
4. 14 Partitioning, Sharding, and Consistent Hashing expert Hash rings, Postgres hash versus list partitioning, and the UUID dedup-table benchmark.
5. 15 Distributed Concurrency, Locking, and Race Conditions expert The portfolio-value debug: optimistic locking, idempotency keys, and database transactions versus in-memory state.

Where state lives and moves: PostgreSQL at scale, Kafka, Kafka Streams, and Redis cluster for real-time fan-out.

1. 16 PostgreSQL at Brokerage Scale expert MVCC, vacuum and autovacuum, index bloat, partial indexes, partition pruning, and long-running-transaction hazards.
2. 17 Kafka as the System of Motion expert Partitions, key ordering versus offset ordering, consumers, and exactly-once semantics at Trade Republic scale.
3. 18 Kafka Streams for Stateful Transforms expert Topologies, state stores, and the real-time compute pattern behind yield-to-maturity streaming.
4. 19 Redis Cluster, Pub/Sub, and Real-Time Fan-Out expert Sharded Pub/Sub, single-connection multiplexing, and the SharedFlow fan-out pattern.

The real interview system-design problems: notifications, order matching, real-time market data, search, and scalable ingestion.

1. 20 Design a Real-Time Notification System expert Millions of users, price-alert plus trade-execution plus market-news fan-out, and latency and reliability tradeoffs.
2. 21 Design an Order Matching Engine expert Full architecture, accounts and holdings consistency, high-frequency correctness, and the defense a Staff engineer expects.
3. 22 Design Real-Time Market Data Streaming to Clients expert Kafka Streams to Redis to WebSocket pipeline, generalized from the yield-to-maturity architecture.
4. 23 Design Scalable Price-Quote and Instrument Search expert Elasticsearch retrieval, recommendations, and a sub-40-millisecond latency budget.
5. 24 Design Event-Driven Horizontally Scalable Ingestion expert Countering the monolithic-ingestion failure mode with partitioned batch workers on Kubernetes.
6. 25 Putting It Together: A Senior's End-to-End Mental Model expert Synthesizing the path from a product tap to a durable, regulated, real-time execution.

The algorithm families the interview evaluates: sliding windows, streaming order statistics, windowed aggregation, and concurrency bug hunting.

1. 26 Sliding Window Algorithms at High Throughput advanced VWAP over a window, ring buffers versus evicting structures, and memory bounds under high arrival rates.
2. 27 Streaming Order Statistics advanced Streaming median with the two-heap pattern and reservoir and fractional techniques.
3. 28 Windowed Aggregation over Event Streams advanced Net portfolio value over a time window, windowed sums, and monotonic-clock pitfalls.
4. 29 Concurrency Bug Hunting and Testing advanced The portfolio-value race condition debug, hypothesis-driven debugging, and property testing.

The senior operating model Trade Republic screens for: ownership, influence, communication, and mission fit.

1. 30 The Behavioral Signals Trade Republic Grades intermediate Ownership, influencing dissent, conflict resolution, and mission alignment as scored signals.
2. 31 Influencing Stakeholders Under Disagreement intermediate The architecture-forum dynamic, RFC-driven persuasion, and data over opinion.
3. 32 Ownership of Ambiguous, Out-of-Scope Problems intermediate The senior operating model at an autonomy-first organization.
4. 33 Communicating Technical Tradeoffs to a Staff Engineer intermediate The defense skill: naming alternatives, costs, and failure modes aloud.
5. 34 Motivation and Mission Fit for Trade Republic intermediate What a credible why-Trade-Republic answer sounds like, tied to democratizing investing.