Software Engineer · Online Assessment · System Design

Anthropic — Software Engineer

Level: Staff-Level

Round: Online Assessment · Type: System Design · Difficulty: 7/10 · Duration: 60 min · Interviewer: Neutral

Topics: System Design, Cloud Storage

Location: Mountain View, CA

Interview date: 2026-01-31

Summary

I was given a system design problem to design a cloud storage system.

Details

The coding question I got was:

class CloudStorage {
    /**
     * Adds a new file with the given `name` and `size` (in bytes) to the storage.
     * If a file with the same `name` already exists, the operation fails.
     * Returns `true` if the file is successfully added, `false` otherwise.
     */
    boolean addFile(String name, int size) {
        // Implementation details
    }

    /**
     * Creates a duplicate of the file at `sourceName` and saves it as `targetName`.
     * Fails if `sourceName` does not exist.
     * Fails if `targetName` already exists.
     * Returns `true` if the copy succeeds, `false` otherwise.
     */
    boolean copyFile(String sourceName, String targetName) {
        // Implementation details
    }

    /**
     * Returns the size of the file in bytes.
     * If the file does not exist, return `-1`.
     */
    int getFileSize(String name) {
        // Implementation details
    }
}

My approach:

1. First, I analyzed the requirements, focusing on scalability and consistency.
2. I decided to use a distributed object storage system, like Amazon S3, as the underlying storage.
3. I implemented the addFile method by checking if the file exists, and then uploading it to the object storage.
4. The copyFile method involves retrieving the source file from object storage and writing it to a new location with the target name.
5. The getFileSize method retrieves metadata from the object storage.

Key insights:

• Scalability is important due to the potential for a large number of files and operations.
• Consistency should be addressed, especially in a distributed environment.