← Google Interview Insights

Google·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
May 2026

Summary

Google phone screen for a software engineering role. The bar was higher than I expected for a phone screen, lots of focus on clean OOP design and trade-off reasoning, not just getting to a working solution.

Questions Asked (1)

Q1

Design and implement a text editor or bookkeeping system, with attention to clean OOP design, data structure trade-offs including memory usage, and accurate time/space complexity analysis.

Algorithms & Data StructuresTechnical Trade-offsSystem Design
Author's notes

The implementation part felt manageable but they pushed hard on why I chose the data structures I did, specifically around memory.

Create a free account to read the full note

AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and choosing a concrete system (text editor or bookkeeping) to design. Then walk through the core data structures and OOP design, explicitly comparing trade-offs in memory and time complexity, and justify your choices. Finally, outline implementation details and potential optimizations.

Pro tip: Demonstrate awareness of real-world constraints by discussing how your design would scale and handle edge cases, and be prepared to write pseudocode for critical operations. Show that you can balance theoretical complexity with practical engineering concerns.

1. Clarify Requirements and Scope

Ask clarifying questions to understand the expected features, scale, and constraints (e.g., concurrent access, persistence, undo/redo). Define the core operations and non-functional requirements.

2. Propose High-Level Design

Sketch the main components and their interactions using OOP principles (e.g., classes, interfaces, inheritance). Choose a system (text editor or bookkeeping) and outline its architecture.

3. Select Data Structures and Analyze Trade-offs

For each core operation, propose data structures (e.g., gap buffer, piece table, balanced BST, hash map) and compare their time/space complexities and memory usage. Justify your choices based on requirements.

4. Detail Implementation and Complexity

Explain how key operations (insert, delete, search, undo) are implemented, including pseudocode if needed. Provide precise time and space complexity analysis for each operation.

5. Discuss Extensions and Optimizations

Address scalability, concurrency, persistence, and potential optimizations. Mention how you would test and validate the design.

Key Points to Mention

  • Trade-offs between data structures (e.g., array vs linked list vs balanced tree) in terms of time complexity and memory overhead.
  • OOP design principles: encapsulation, inheritance, polymorphism, and design patterns (e.g., Command pattern for undo/redo).
  • Time and space complexity analysis for core operations (insert, delete, search, undo) using Big-O notation.
  • Memory usage considerations: overhead of pointers, fragmentation, and strategies like gap buffers or piece tables for text editors.
  • Handling edge cases: empty input, large data, concurrent modifications, and error handling.
  • Scalability and performance: indexing, caching, and potential use of persistent data structures.

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