Susquehanna International Group Software Engineer
Interview Guide

Movie Catalog Search & Indexing: Given a list of movies with attributes (title, release year, category), implement a catalog and optimize search queries so elements within a specific range can be returned in $O(\log N)$ or $O(1)$ time using appropriate indexing and dynamic maps.

News Headline Ticker Search: Given a mapping of company names to stock tickers (e.g., "The Big Company" $\rightarrow$ TBC), write a system to match and return all valid tickers mentioned in a given news headline, correctly handling substring overlap (e.g., matching both "Cool Company" and "My Super Cool Company").

Trie-Based Prefix Search & String Parsing: Implement an efficient Trie data structure to handle high-speed string lookup, prefix matching, and string compression algorithms (e.g., encoding AAABBCC to A3B2C2).

Matrix and Stack Operations: Solve array and matrix transformation problems, including sliding window algorithms over streaming data, min-heap top-$K$ element queries, dynamic programming, and $2\text{D}$ matrix grid manipulation.

Stateful Financial Ledger & Delayed Operations: Implement a bank account simulation class supporting basic deposit and withdraw operations, extending it to track and process delayed operations, such as automatically applying a $2%$ cashback credit exactly 24 hours after a withdrawal.

In-Memory File System: Design an in-memory file system (equivalent to standard memory file management APIs) supporting path creation, directory listing, file reads, and file content appends with clean class abstractions.

Order Book & Financial Exchange Simulation: Design an order book data structure handling bid and ask matching, evaluating the performance trade-offs of binary search trees, min/max heaps, vectors, and hash maps for high-speed search and insertion.

Library & Asset Search System: Model an extensible domain system for cataloging physical or digital assets, ensuring proper implementation of standard object-oriented design patterns, encapsulation, and interface segregation.

Custom Vector Implementation: Re-implement a lightweight version of std::vector (or equivalent dynamic array) from scratch. Explain allocation strategy, dynamic resizing logic, dynamic memory allocation costs, and exception guarantees.

Language Trade-Offs (C# vs. Java vs. C++): Compare language runtime execution environments, focusing on Garbage Collection (GC) pauses versus manual memory management, Just-In-Time (JIT) compilation, allocation overhead, and execution efficiency in financial trading platforms.

Pointers, References, and Memory Layout: Explain memory alignment, cache line friendliness, cache misses, and pointer-to-hash-map data structures when designing low-latency processing systems.

A tenant on the standard plan may hold at most 50 resources with status='active'. The create handler runs SELECT count(*) FROM resource WHERE tenant_id = $1 AND status = 'active', compares to 50, then inserts. Two creates arrive 3 ms apart on different instances and the tenant lands at 51. Name the anomaly, say whether PostgreSQL 16 READ COMMITTED or REPEATABLE READ prevents it and why, then give an implementation that holds the cap at READ COMMITTED with the exact statements. Finally, say what changes when the cap is 'at most one running export per tenant' on job_run.

resource_revision (revision_id, resource_id, version, actor_user_id, change_kind, patch, request_id, created_at) has 400M rows and no tenant column; tenant_id lives only on resource. Two reads need it: a tenant-scoped audit feed ordered by created_at DESC, and an offboarding purge. Both join back to resource today. Justify adding tenant_id to resource_revision against those two reads, name the anomaly the copy introduces and the constraint that prevents it, then give the ordered migration for a live table taking 1.2k writes/second — the lock each step takes, how the backfill is batched, and where each step stops being reversible. PostgreSQL 16.

Grocery Checkout System: Design a Point-of-Sale (POS) and checkout system supporting item inventory, weight/unit pricing, coupon applications, dynamic receipt generation, and extensible membership rewards integration.

std::vector::push_back and Move Semantics: Walk through the mechanical execution of std::vector::push_back, detailing capacity doubling, amortized $O(1)$ complexity, copy versus move constructors, Rvalue references, and Empty Base Optimization (EBO).

The tenant listing endpoint reads resource filtered by tenant_id and status, ordered by updated_at DESC, and returns each row plus the owner's display name from app_user and the actor of that resource's latest resource_revision. p99 is 55 ms at 10 rows per page and 1.4 s at 200. Database telemetry shows 401 statements per request, each under 1 ms, and nothing in the slow-query log. Diagnose the cause and give the fix, stating the statement count per request and the p99 you expect afterwards.