Grokking the Machine Learning Interview: A Comprehensive Guide

So you want to ace that machine learning interview, huh? It's not as daunting as it seems, especially if you know what to expect.

The interview process typically starts with a phone screen, where the interviewer will ask you to explain your experience with machine learning concepts, such as supervised and unsupervised learning, and how you would approach a problem like image classification.

You'll also be asked to walk through a case study, like the one where you were tasked with predicting customer churn based on historical data, which involved selecting relevant features and using a classification algorithm.

To prepare, it's essential to review common interview questions, such as "What's the difference between a neural network and a decision tree?" or "Can you explain the concept of overfitting?"

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To prepare for the machine learning interview, you need to be motivated and willing to put in the effort to learn and practice. A typical MLE interview loop consists of 6 rounds, as shown in the hexagon, with some companies using a subset and others having unique rounds.

You'll want to focus on building solid ML foundations, as a successful candidate is a good coder with a strong understanding of machine learning concepts. Good MLEs are indeed unicorns, as Josh Tobin put it, likening them to rare and mythical creatures.

Coding interviews for MLE candidates are like the GRE for Ph.D. candidates - good performance doesn't guarantee acceptance, but poor performance easily disqualifies you. There are 3 styles of MLE coding questions: coding, ML System Design, ML Breadth, ML Domain Knowledge, Project Deep Dive, and Behavior Interview.

To improve your chances, focus on first-principle thinking in ML System Design, and brush up on ML foundations, including the bias-variance trade-off, detecting overfitting and under-fitting, L1/L2 regularization, feature/model selection, and DL basics.

Here's a breakdown of the typical MLE interview rounds:

Reading and thinking about ML foundations will not only help you prepare for the interview but also make you a more principled and creative decision-maker at work.

Machine learning is a broad field that encompasses various techniques and concepts. One of the fundamental topics in machine learning is supervised learning, which involves training a model on labeled data to make predictions.

Supervised learning can be categorized into classification and regression. Classification involves predicting a categorical label, such as spam or not spam, while regression involves predicting a continuous value, such as a house price. Some common algorithms used in supervised learning include logistic regression, decision trees, and support vector machines.

To implement logistic regression from scratch, you can use the following formula: p = 1 / (1 + e^(-z)), where p is the probability of the positive class and z is the linear combination of features. You can also use libraries like scikit-learn to implement logistic regression.

Another fundamental topic in machine learning is unsupervised learning, which involves finding patterns in unlabeled data. Unsupervised learning can be categorized into clustering and dimensionality reduction. Clustering involves grouping similar data points together, while dimensionality reduction involves reducing the number of features in the data.

A different take: What Is the Difference between Supervised and Unsupervised Machine Learning

Some common algorithms used in unsupervised learning include k-means clustering and principal component analysis (PCA). To implement k-means clustering from scratch, you can use the following formula: c = (1/n) * Σ(x_i), where c is the centroid of the cluster and x_i is the data point.

Here's a summary of the fundamental topics in machine learning:

Understanding these fundamental topics is essential for grokking the machine learning interview. By mastering these concepts, you'll be well-prepared to tackle the challenges of the interview.

System design interviews are a mini design review for an ML project. You need to understand how the model moves the needle of a business goal, how success is measured, and what the system requirements are.

To prepare for a system design interview, take ML system design courses, such as Grokking the Machine Learning Interview. However, these resources don't cover enough ML depth in any given domain, so it's essential to know the industry gold standard, state-of-the-art models, and best practices for ML production in your domain.

Additional reading: System Design Grokking

System design concepts are essential for machine learning engineers. To take this further, any engineer who wants to advance their career must implement machine learning into system design. Almost every system will have an ML component in the next few years.

Interviewers are looking for candidates who understand how recommendation systems work, namely ad suggestions, rideshare clustering, or news feeds. To prove you're a next-gen engineer, you'll need to discuss the technologies and methodologies behind ML components during your interview.

Here are some key system design concepts to focus on:

To drive a system design interview in an organized manner, you need to cover all bases in 45 minutes or 1 hour, while also attuning to the interviewer's preferences. Think of them as design reviewers and meet their requests to get buy-in.

For another approach, see: Grokking System Design Pdf

In a typical machine learning interview, you can expect to be asked to code simple ML algorithms from scratch and run them on toy data. Some common algorithms you might be asked to implement include K-means, logistic/linear regression, and KNN.

You might like: Grokking Algorithms by Aditya Bhargava

You can find example implementations of these algorithms in various online resources, such as the author's blog post. You can also ask your recruiter if you're expecting LC-style coding, ML coding, or both.

To prepare for ML coding questions, you can practice coding for basic models by merging your ML coding preparation with the fundamentals in ML breadth. This can be done by practicing coding for a few days, focusing on basic models and algorithms. Some helpful resources for this include Neetcode's Machine Learning Coding Questions, Github's 100 Days of ML Code, and AlgoExpert's ML Coding Questions.

Discover more: Grokking the Coding Interview

I spent about 35% of my prep time on Machine Learning Breadth, which tests your broad knowledge across various ML topics. This round is a significant part of most machine learning interviews, so it's essential to focus on it.

To prepare for this round, I recommend dedicating a substantial amount of time to studying machine learning fundamentals, including topics like supervised and unsupervised learning, neural networks, and deep learning.

Here's a breakdown of how I allocate my prep time across the different rounds:

Keep in mind that this breakdown will vary depending on your experience level and background, so be sure to adapt your preparation strategy to best fit your needs.

Coding is a crucial part of any machine learning interview. You may be asked to code simple ML algorithms from scratch and run them on toy data, including K-means, logistic/linear regression, and KNN.

Some companies may not ask you to write a full algorithm, but rather a model component, operation, or evaluation metric. You can find example implementations in various resources, such as my blog post or ML Code Challenges.

ML coding is uncommon, but more frequently seen in startups. If you're expecting an ML coding round, confirm with your recruiter and reallocate some time from ML breadth to practice coding for a few days.

To prepare for ML coding, you can practice coding for basic models and merge your ML coding preparation with the fundamentals in ML breadth. Use resources like Neetcode, Github, Kaggle, and AlgoExpert to help you prepare.

You might like: Grokking the Coding Interview Pdf

Here are some specific resources to check out:

ML Cheatsheet and ML Interview book by Chip Huyen are also great resources for quick revisions and learning more about ML coding.

Before diving into model training, it's essential to clarify the details of your data. Start by identifying what data is available for your project, and consider how to preprocess it to ensure it's clean and structured correctly. This may include handling missing values, normalizing or scaling features, and removing any irrelevant or duplicate data.

To ensure accurate results, consider the structure of your data and avoid random splitting when there's a time dependency. For example, training a model on this year's stock prices and validating on last year's would give inaccurate results.

To get started with model training, it's crucial to have a solid baseline. Don't jump straight to the fanciest models - start with a simple one and iterate quickly to test your hypotheses. This will help you understand encoding methods for each type of data, such as categorical, numerical, text, and images, and how to combine them effectively.

Here are some key considerations for model training:

Model training is a crucial step in the machine learning process, and it's essential to get it right. You need to check everything carefully before diving into solutions.

To start, you should establish a solid baseline for your model. Don't jump straight to the fanciest models - iterate quickly to test your hypotheses and refine your approach.

Understanding how to represent different types of data is also crucial. This includes encoding methods for categorical, numerical, text, and image data, as well as how to combine them effectively.

Different tasks require different loss functions, so it's essential to understand each one's weak spots and how to address them. For example, imbalance is common in classification tasks, and you can address it with oversampling, data augmentation, or weighted loss functions.

To get a complete picture of the model's quality, it's a good idea to pick different offline metrics. This will help you find the best approach and ensure that your model is robust.

Finally, be aware of how to handle changing distributions due to seasonality, global events, or holidays. Avoid training your model only on data from specific times, as this can lead to issues when using the model year-round.

A fresh viewpoint: Is Transfer Learning Different than Deep Learning

Data is a crucial part of the model training process, and it's essential to identify what data is available for your project. This can include user behavior logs, purchase records, and browsing patterns.

Having access to relevant data can make all the difference in training an effective model. For instance, an online store might use data on user behavior to train a model that generates outfit suggestions for dog owners who buy clothes for their pets on Halloween.

To ensure your data is clean and structured correctly, preprocess it by handling missing values, normalizing or scaling features, and removing any irrelevant or duplicate data.

Data preprocessing is an iterative process, and it may take some trial and error to get it just right. But trust me, it's worth the effort.

Here are some common data preprocessing tasks to consider:

When splitting your data, consider the structure of your data and avoid random splitting when there's a time dependency. For example, training a model on this year's stock prices and validating on last year's would give inaccurate results.

Remember, the goal of data preprocessing is to create a clean and structured dataset that's ready for model training.

A fresh viewpoint: Ai and Machine Learning Training