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Lead Applied Machine Learning Scientist

  • Boston, MA
  • Data Science

At Klaviyo, we value the unique backgrounds, experiences and perspectives each Klaviyo (we call ourselves Klaviyos) brings to our workplace each and every day. We believe everyone deserves a fair shot at success and appreciate the experiences each person brings beyond the traditional job requirements. If you’re a close but not exact match with the description, we hope you’ll still consider applying. Want to learn more about life at Klaviyo? Visit to see how we empower creators to own their own destiny.

About the team:

Klaviyo operates a real-time data analytics platform coded primarily in Python that is built for massive scale and hosted on Amazon Web Services (AWS). Engineers come to Klaviyo with experience in a variety of languages and from a number of disciplines.

At Klaviyo, we love tackling tough engineering problems and look for employees who specialize in certain areas but are passionate about building, owning & scaling features end to end from scratch and breaking through any obstacle or technical challenge in their way. We push each other to move out of our comfort zone, learn new technologies, and work hard to ensure each day is better than the last. Learn more about our engineering culture at

About the role:

About the role:

The Lead Machine Learning Engineer will help build foundational models at Klaviyo that extract insights from the massive streams of data that Klaviyo ingests continuously. You will apply cutting edge techniques from deep learning, language modeling, recommender systems, and more to generate value for our customers by allowing them to target and personalize their messages. You have capable software engineering skills and must be able to lead the entire model lifecycle from inception to production. 

You will be a technical leader within the organization, helping to set the standard for excellence in areas including software code quality, engineering best practices, machine learning performance. You will amplify your own impact by mentoring other team members on technical skills.

You have in depth experience in machine learning and have already trained and developed multiple advanced models in the recommender, NLP, or related areas working with massive data sets. You are determined, motivated, and ready to overcome new challenges to build the best solutions.

This role is based out of Boston, MA and requires a weekly, hybrid in-office component. 

How you'll have an impact:

30 days 

  • You will have finished on-boarding including engineering and data science specific on-boarding.

  • Your local developer environment is set up and usable.

  • You will have met multiple members of the Data Science team and are starting to familiarize yourself with both the Klaviyo product and the data sources available to you.

60 days 

  • You will understand how to train and test models in Klaviyo. 

  • You will have developed an opinion about what’s needed to tackle your initial project including the data needed, the success metrics, the technical approach, the experiments needed to test performance in production, etc. 

  • You will have participated in at least 1 review for a project that a teammate is running and able to share your knowledge

90 days

  • You will be actively iterating on models for your first project, and have identified opportunities and obstacles to progress with plans to address them. 

  • You will be actively working with teammates across Data Science to accelerate progress.

  • In partnership with your manager, you will be regularly in conversation with Product and Engineering stakeholders to make sure work remains aligned with company priorities.

Up to 1 year 

  • You will have developed multiple impactful models that use Klaviyo’s data, which have been put into production and are generating value in novel and powerful ways for our customers.

  • You are regarded as a technical leader and have introduced new techniques to Klaviyo’s toolset that are being used by other data scientists. 

  • You continue to deliver new and innovative solutions to ML problems that Klaviyo faces and find new ways to generate value for our customers from Klaviyo’s data.

What we’re looking for:

  • 8+ years industry experience in machine learning or data science where you have led the development of complex models on massive data sets that power customer-facing features
  • Experience writing code to high software engineering standards, following best practices such as test-driven development, code review, etc
  • Ability to develop technical roadmaps for solving complex business problems using ML
  • Experience in at least one of NLP or recommender systems
  • Experience working with Transformers or other deep learning models
  • Experience interacting with databases, REST interfaces, and other modern SaaS development patterns
  • Experience mentoring others

Nice to have:

  • Personally put models into production, monitored and maintained them in production
  • Experience with frameworks such as Huggingface, PyTorch, Tensorflow, Keras
  • Experience with distributed training with Spark, Ray, etc.
  • Experience working with customers directly
  • Experience working with Product orgs

#LI-Onsite   #LI-CB2

The pay range for this role is listed below. Sales roles are also eligible for variable compensation and hourly non-exempt roles are eligible for overtime in accordance with applicable law. This role is eligible for benefits, including: medical, dental and vision coverage, health savings accounts, flexible spending accounts, 401(k), flexible paid time off and company-paid holidays and a culture of learning that includes a learning allowance and access to a professional coaching service for all employees.

Base Pay Range For US Locations:
$192,000—$288,000 USD

Get to Know Klaviyo

We’re Klaviyo (pronounced clay-vee-oh). We empower creators to own their destiny by making first-party data accessible and actionable like never before. We see limitless potential for the technology we’re developing to nurture personalized experiences in ecommerce and beyond. To reach our goals, we need our own crew of remarkable creators—ambitious and collaborative teammates who stay focused on our north star: delighting our customers. If you’re ready to do the best work of your career, where you’ll be welcomed as your whole self from day one and supported with generous benefits, we hope you’ll join us.

Klaviyo is committed to a policy of equal opportunity and non-discrimination. We do not discriminate on the basis of race, ethnicity, citizenship, national origin, color, religion or religious creed, age, sex (including pregnancy), gender identity, sexual orientation, physical or mental disability, veteran or active military status, marital status, criminal record, genetics, retaliation, sexual harassment or any other characteristic protected by applicable law.

IMPORTANT NOTICE: Our company takes the security and privacy of job applicants very seriously. We will never ask for payment, bank details, or personal financial information as part of the application process. All our legitimate job postings can be found on our official career site. Please be cautious of job offers that come from non-company email addresses (, instant messaging platforms, or unsolicited calls. 

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