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Google·Software Engineer·Technical Phone Screen·Senior

Senior
Apr 2026

Summary

Google ML round for a software engineering role, split between a resume walkthrough and a fairly deep dive into LLM and generative AI fundamentals. The technical portion leaned heavily on knowing the tradeoffs between fine-tuning approaches and understanding generative architectures at a conceptual level, not just name-dropping them.

Questions Asked (5)

Q1

Walk me through your resume and relevant experience.

Adaptability & Ambiguity
Author's notes

Standard opener, took about ten minutes.

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AI HintsAI Generated

Suggested Approach

Structure your answer as a concise narrative that highlights your technical growth and adaptability, focusing on experiences most relevant to Google's engineering culture. Use the 'Present-Past-Future' formula: start with your current role, then walk through key past experiences that demonstrate impact and learning, and end with why you're excited about this opportunity.

Pro tip: Quantify your impact with specific metrics (e.g., 'reduced latency by 30%') and explicitly connect each experience to Google's values like scalability, innovation, or user focus. Avoid simply listing jobs; instead, tell a story of increasing responsibility and problem-solving.

1. Present: Current Role and Key Achievements

Briefly describe your current position, emphasizing projects and technologies that align with the role. Highlight 1-2 major accomplishments with measurable results.

2. Past: Relevant Experience and Growth

Walk through previous roles in reverse chronological order, focusing on experiences that demonstrate adaptability, technical depth, and impact. Connect each role to the skills required for this position.

3. Highlight Adaptability and Ambiguity

Emphasize situations where you navigated unclear requirements, learned new technologies quickly, or pivoted successfully. Show how you thrive in dynamic environments.

4. Future: Why This Role and Company

Explain how your background prepares you for this specific role and why you're excited about Google's mission and engineering challenges. Align your goals with the company's needs.

Key Points to Mention

  • Specific technical skills and projects that match the job description (e.g., distributed systems, algorithms, cloud computing).
  • Quantifiable achievements (e.g., improved performance by X%, led a team of Y engineers).
  • Examples of adapting to new technologies or ambiguous situations, showing flexibility and problem-solving.
  • Collaboration and leadership experiences, especially in cross-functional teams.
  • Continuous learning and passion for software engineering (e.g., side projects, open-source contributions).
  • Alignment with Google's values: innovation, scalability, user focus, and making an impact.

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

Q2

What are the main LLM fine-tuning methods, and how do you decide which one to use for a given situation?

Technical Trade-offsSystem Design
Author's notes

This is where things got real.

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AI HintsAI Generated

Suggested Approach

Start by categorizing fine-tuning methods into full fine-tuning, parameter-efficient fine-tuning (PEFT) like LoRA and adapters, and prompt-based approaches. Then walk through a decision framework based on task complexity, data availability, compute budget, and latency requirements, emphasizing trade-offs. Conclude with a concrete example of how you would choose for a specific scenario.

Pro tip: Mention that you always start with the simplest approach (e.g., prompt engineering or few-shot learning) and only escalate to fine-tuning when necessary, as it saves resources and reduces overfitting risk. Also, highlight that you consider evaluation metrics and potential catastrophic forgetting when choosing a method.

1. Categorize fine-tuning methods

Briefly list the main categories: full fine-tuning, PEFT (e.g., LoRA, prefix tuning, adapters), and prompt-based methods (soft prompts, prompt tuning). Mention that each has sub-variants and trade-offs.

2. Identify decision factors

Outline key factors: task complexity, dataset size, compute resources, inference latency, and deployment constraints. Explain how each factor influences the choice.

3. Map factors to methods

Describe how to match factors to methods: e.g., full fine-tuning for high-resource, high-accuracy needs; PEFT for limited compute or multiple tasks; prompt tuning for few-shot scenarios.

4. Discuss trade-offs and best practices

Highlight trade-offs like performance vs. efficiency, and best practices like starting simple, using evaluation metrics, and monitoring for catastrophic forgetting.

5. Provide a concrete example

Walk through a specific scenario (e.g., adapting an LLM for a customer service chatbot) and justify your method choice based on the factors discussed.

Key Points to Mention

  • Full fine-tuning: updates all model parameters, high resource cost, best for large datasets and high accuracy.
  • Parameter-efficient fine-tuning (PEFT): methods like LoRA, adapters, prefix tuning; update few parameters, lower compute, suitable for limited resources or multi-task.
  • Prompt-based methods: soft prompts, prompt tuning; no parameter updates, good for few-shot, but may underperform on complex tasks.
  • Decision factors: task complexity, dataset size, compute budget, inference latency, deployment constraints, and need for multi-task support.
  • Trade-offs: performance vs. efficiency, risk of catastrophic forgetting in full fine-tuning, and inference overhead in some PEFT methods.
  • Best practice: start with prompt engineering or few-shot learning, then escalate to PEFT, and only use full fine-tuning when necessary.

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

Q3

You're fine-tuning a model on a small dataset and notice performance on the original task has degraded. How do you approach this?

Technical Trade-offsRoot Cause Analysis
Author's notes

Catastrophic forgetting question dressed up as a scenario.

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AI HintsAI Generated

Suggested Approach

Start by acknowledging the problem as catastrophic forgetting and outline a systematic debugging process. Then describe how you would diagnose the cause by comparing training and evaluation metrics, and finally present a set of mitigation strategies with trade-offs.

Pro tip: Mention that you would first check if the degradation is due to overfitting on the small dataset or forgetting, and consider using techniques like elastic weight consolidation or rehearsal. Also, emphasize the importance of establishing a baseline and monitoring metrics throughout fine-tuning.

1. Identify and Quantify the Degradation

Measure the performance drop on the original task using a held-out validation set. Compare metrics before and after fine-tuning to confirm the issue.

2. Diagnose the Root Cause

Determine if the degradation is due to catastrophic forgetting, overfitting to the small dataset, or hyperparameter issues. Analyze training curves and evaluate on both tasks.

3. Explore Mitigation Strategies

Consider approaches like regularization (e.g., L2, dropout), elastic weight consolidation, rehearsal (mixing original data), or parameter-efficient fine-tuning (e.g., adapters, LoRA).

4. Implement and Evaluate Solutions

Choose a strategy based on constraints, implement it, and re-evaluate on both tasks. Iterate until a satisfactory trade-off is achieved.

5. Monitor and Prevent Future Occurrences

Set up continuous evaluation on both tasks and use techniques like early stopping or multi-task learning to maintain performance.

Key Points to Mention

  • Catastrophic forgetting and its causes
  • Overfitting on small datasets and regularization techniques
  • Elastic weight consolidation (EWC) or similar continual learning methods
  • Rehearsal or replay of original task data
  • Parameter-efficient fine-tuning methods (e.g., LoRA, adapters)
  • Importance of validation sets and metric tracking

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

Q4

How much data do you actually need to fine-tune an LLM effectively, and what factors influence that number?

Technical Trade-offsAlgorithms & Data Structures
Author's notes

Blanked for a second on this one.

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AI HintsAI Generated

Suggested Approach

Acknowledge that there is no fixed number—it depends on the base model, task complexity, and desired performance. Structure your answer by first explaining the key factors, then giving rough ranges for different scenarios (e.g., simple classification vs. complex generation), and finally discussing trade-offs and evaluation methods.

Pro tip: Emphasize that data quality and diversity often matter more than quantity, and mention that parameter-efficient methods like LoRA can achieve strong results with far less data than full fine-tuning.

1. Clarify the goal and constraints

Start by defining what 'effectively' means for the specific use case—target metrics, latency, and compute budget. This frames the data requirement discussion.

2. Identify key factors

List factors such as base model size and pretraining, task complexity, fine-tuning method (full vs. PEFT), and data quality/diversity.

3. Provide rough ranges

Give ballpark figures: e.g., 100–1,000 examples for simple classification with PEFT, 10k–100k for complex generation, and millions for full fine-tuning from scratch.

4. Discuss trade-offs and evaluation

Explain how more data can lead to diminishing returns and how to use learning curves and validation performance to find the sweet spot.

5. Conclude with a practical recommendation

Suggest starting small with high-quality data, iterating based on evaluation, and scaling up only if needed.

Key Points to Mention

  • Base model size and pretraining: larger models often need less data for a given task due to better generalization.
  • Task complexity: simple classification may need hundreds of examples, while complex generation or reasoning may need thousands to millions.
  • Fine-tuning method: full fine-tuning typically requires more data than parameter-efficient methods like LoRA or adapters.
  • Data quality and diversity: high-quality, diverse examples can reduce the required quantity.
  • Evaluation metrics and learning curves: use validation performance to determine when adding more data yields diminishing returns.
  • Compute and time constraints: practical limits often dictate the feasible amount of data and method.

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

Q5

Compare autoencoders, variational autoencoders, and VQ-VAEs. What are the differences in their objectives and latent representations?

Technical Trade-offsSystem Design
Author's notes

Genuinely enjoyed this one.

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AI HintsAI Generated

Suggested Approach

Start by defining the core objective of each model: autoencoders for reconstruction, VAEs for probabilistic generation, and VQ-VAEs for discrete representation learning. Then contrast their latent spaces (deterministic continuous, continuous probabilistic, discrete codebook) and discuss trade-offs in terms of training stability, sample quality, and use cases. Finally, relate these differences to practical applications like image generation, compression, and representation learning.

Pro tip: Emphasize that VQ-VAEs address posterior collapse in VAEs by using a discrete codebook, which often yields more meaningful and disentangled representations—a key insight for system design at Google.

1. Define Objectives

State the primary objective of each model: autoencoders minimize reconstruction error, VAEs maximize the evidence lower bound (ELBO) for generative modeling, and VQ-VAEs combine reconstruction with vector quantization to learn discrete latent codes.

2. Describe Latent Representations

Explain that autoencoders have a deterministic continuous latent vector, VAEs have a continuous probabilistic latent (typically Gaussian), and VQ-VAEs have a discrete latent space defined by a codebook of embeddings.

3. Compare Training and Losses

Detail the loss functions: autoencoders use reconstruction loss (e.g., MSE), VAEs add KL divergence to regularize the latent distribution, and VQ-VAEs use reconstruction loss plus codebook and commitment losses to align encoder outputs with codebook vectors.

4. Discuss Trade-offs and Use Cases

Highlight trade-offs: autoencoders are simple but not generative; VAEs generate diverse samples but may suffer from blurriness and posterior collapse; VQ-VAEs produce sharp samples and discrete codes but can suffer from codebook collapse. Mention applications like image generation, compression, and discrete representation learning.

5. Summarize Key Differences

Concisely summarize the differences in objectives and latent representations, and optionally mention extensions like hierarchical VAEs or residual VQ.

Key Points to Mention

  • Autoencoders: deterministic continuous latent space, trained with reconstruction loss only.
  • VAEs: probabilistic continuous latent space, trained with reconstruction loss + KL divergence (ELBO).
  • VQ-VAEs: discrete latent space via vector quantization, trained with reconstruction loss + codebook loss + commitment loss.
  • Posterior collapse in VAEs and how VQ-VAEs mitigate it with discrete codes.
  • Trade-offs: sample quality, training stability, and interpretability of latent representations.
  • Applications: autoencoders for dimensionality reduction, VAEs for generative modeling, VQ-VAEs for discrete representation learning (e.g., image generation, speech).

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