Twilio · Primly Community

Twilio machine learning engineer interview: what they're actually testing (hint: not what you'd expect)

ds_dmitri · 4 replies

Finished a Twilio MLE loop in Q1 2026. Sharing because the ML interview landscape varies so much company to company and I had basically no signal going in.

Twilio isn't a model-building company in the same sense as Google Brain or a pure-play AI lab. Their ML work is largely applied: fraud detection, spam filtering on SMS/voice, call quality prediction, intelligent routing. That framing matters a lot for how they interview.

Round 1: ML fundamentals. Talked through classification models, precision vs recall tradeoffs (very relevant for spam filtering use cases), handling class imbalance, and feature engineering. Pretty solid foundational coverage. No take-home, no Kaggle-style problem.

Round 2: ML system design. This was the most interesting round. The prompt: design an ML system to detect fraudulent SMS messages in near-real-time. We had to cover data collection, feature pipeline, model choice, latency constraints, monitoring for model drift, and how you'd retrain. This is where candidates get separated. You can't give a textbook answer here. The latency and scale constraints (Twilio moves a lot of messages) make it a real engineering problem.

Round 3: Coding (Python). One algorithmic problem (arrays/sliding window, medium difficulty), and one problem that was data-manipulation heavy: given a dataset of message delivery events, compute certain aggregations. More applied data work than pure LC.

Round 4: Behavioral. Two rounds actually, one with the hiring manager. They wanted to know about times I drove an ML project end-to-end, how I handled disagreements with product about model deployment decisions, and how I communicated model performance to non-technical stakeholders.

No deep learning required for this role. I barely talked about neural nets. It was more classical ML and pragmatic engineering. If you're coming from a pure research background this might feel different.

Offer was in the $195k-$215k base range for senior MLE, Bay Area. Solid but not hyperscaler numbers.

4 replies

sec_sasha

The "detect fraudulent SMS" design question is a great one because it has all the real complications: highly imbalanced labels, adversarial users who adapt, latency requirements, and a feedback loop from human reviewers. How deep did they go on the monitoring and retraining piece specifically?

ml_mike

Fairly deep. I proposed a sliding window approach to catch drift on key distribution metrics (feature distributions, model output distributions), and we talked through whether to do scheduled retraining vs triggered retraining. They seemed most interested in how I'd define the monitoring signals before the model actually degrades.

ae_andre

The data manipulation coding problem makes a lot of sense for what Twilio's infra team would actually do. Aggregate delivery events, compute SLAs, identify latency outliers. Way more representative than a graph traversal problem for an MLE role.

sdr_sky

Did they ask anything about feature stores or MLOps tooling, or was it more focused on the modeling side?