Goldman Sachs·Software Engineer·Onsite - System Design / Architecture·Senior

SeniorPrefer not to say

Jun 2026

Summary

System design round at Goldman Sachs for a SWE role. Just one question but it took up the whole session and went deeper than I expected.

Questions Asked (1)

Design a version control system like Git.

System DesignData ModelingTechnical Trade-offs

Author's notes

I started with the basics, blobs, trees, commits, and thought I was doing fine.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and scope, then focus on the core data model (content-addressable storage, DAG of commits) and key operations (commit, branch, merge). Discuss trade-offs in storage, performance, and consistency, and relate to Goldman Sachs' needs for auditability and reliability.

Pro tip: Emphasize how Git's immutable, content-addressable design provides a natural audit trail and data integrity—critical for financial systems. Also, mention that you'd consider integrating with existing CI/CD and access control systems.

1. Clarify Requirements and Scope

Ask about expected scale (number of repos, users, file sizes), consistency needs, and specific features (branching, merging, history). Confirm whether to design a full Git clone or a simplified version.

2. Design Core Data Model

Define objects: blobs (file contents), trees (directories), commits (snapshots with metadata), and refs (branches/tags). Use content-addressable storage with SHA-1 hashes for integrity and deduplication.

3. Define Key Operations and APIs

Outline operations: commit, branch, checkout, merge, clone, fetch, push. Describe how they manipulate the object graph and update refs, ensuring atomicity and conflict resolution.

4. Address Storage and Performance

Discuss packfiles for compression, delta encoding, and garbage collection. Consider distributed storage (e.g., S3) for scalability and caching for performance.

5. Discuss Trade-offs and Extensions

Compare centralized vs. distributed models, consistency vs. availability, and security (access control, encryption). Mention potential integrations with CI/CD and audit systems.

Key Points to Mention

Content-addressable storage using SHA-1 hashes ensures data integrity and deduplication.
The commit DAG enables efficient branching, merging, and history traversal.
Packfiles and delta compression optimize storage and network transfer.
Distributed architecture allows offline work and resilience, but introduces merge conflicts.
Access control and audit logging are essential for enterprise environments like Goldman Sachs.
Trade-offs between consistency (e.g., strong vs. eventual) and performance in a distributed system.

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.