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Senior Software Engineer, SMS International

  • London, UK
  • Engineering

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.

Klaviyo is growing by leaps and bounds; as a result, we’ve recently established our SMS International team! With the explosive growth of SMS as a channel for customer communication, Klaviyo’s SMS offering is on the path toward market dominance. This team will focus on building and scaling a world-class messaging platform across the world. 

As a Senior Software Engineer joining the SMS International team you can expect to be deeply involved in technical discussions on how we scale our systems, build out and monitor new features, and help build the team. Another big focus of the role will be to build functionality that is reusable and extensible so that we can launch SMS in countries quickly.

The role will allow you to work with multiple stakeholders to provide the best in class service and reliability to connect a wide range of customers, from entrepreneurs to enterprises, with their end users. The messaging platform for Klaviyo delivered over 71 million SMS messages and 5.5 billion emails during BFCM 2022 (Black Friday/Cyber Monday). 

Engineers come to Klaviyo with experience in a variety of languages and from a number of disciplines. Technologies we use (not exhaustive): 

  • Python, Django, Celery
  • MySQL, Cassandra, RabbitMQ, Redis, Pulsar
  • React, Typescript, Front end best practices
  • Amazon Web Services (EC2, RDS, Aurora, etc.), Fastly Cache, Kubernetes
  • Twilio, Sendgrid, Firebase, APNS

How You Will Make a Difference 

  • Build and improve systems for high volume message delivery using multiple engagement channels. 
  • Provide technical leadership to drive architectural decisions across multiple teams and provide solutions for complex problems around scalability, throughput, performance etc.
  • Strive towards a cohesive technical vision across multiple roadmap items that are built across multiple teams.
  • Be a technical point of contact for the team for various projects and features where there are dependencies.
  • Defines technical strategy within their scope and executes to improve the functional area's products, infrastructure, or processes.
  • Support EMs and PMs within the organisation from a technical point of view.
  • Mentors multiple engineers to develop new technical leadership for the company.

Who You Are 

  • Have 5-7 years of experience in software engineering with a significant part as a full stack developer.
  • Experienced with cloud-based systems development and deployment, AWS preferred.
  • Experience working with both monolithic and microservices architectures.
  • Experience with creating and refactoring databases that can withstand high query volumes.
  • Proven experience with being a coach and a mentor for team members and helping them grow
  • You have working knowledge of object-oriented design principles.
  • Love digging into performance and scalability issues to drive breakthrough solutions--whether it's a slow loading UI or too many clicks in a workflow, a database query timing out, or a queue that just won’t drain. You recognize all problems can be solved.
  • Enjoy shipping code early & often in an agile fashion, pairing with product management to craft better software by soliciting feedback from thousands of end users. 
  • Authorisation to work in the UK without restriction.

Klaviyo in EMEA

London was our first non-US location for Klaviyo, opening up in 2019 and growing since then to a large team of people with teams across Sales, Customer Success, Marketing, Services, Partnerships, IT and HR. Collectively in EMEA we are contributing a significant part of Klaviyo’s overall global success, growth to date and opportunity that lies ahead. The good news is that we are still at a stage where everyone coming into the business has the opportunity to make a real tangible impact that you will be able to see and feel.

We are proud of everything we have built here in EMEA, a vibrant diverse team embracing hybrid working in line with the way the world of work has changed. When Klaviyos do travel to the office you’ll be able to use your monthly commuter allowance if you need it. Once here you'll be able to enjoy the comforts of an incredible environment with all the perks we love and you’d expect such as, free snacks / drinks, a peloton studio and a roof terrace overlooking the city to rival anything you’d find in London as well as regular team celebrations and company lunches.

As part of the Klaviyo team you will be looked after with some great benefits locally in EMEA including equity for all, private health cover for you and discounted for your household, financial and professional coaching, a generous annual learning allowance (£2.5k), 22 weeks full pay primary caregiver leave (16 week secondary) and free books (yes, any books!) to name a few.

Get to Know Klaviyo

Klaviyo is a world-leading marketing automation platform dedicated to accelerating revenue and customer connection for online businesses. Klaviyo makes it easy to store, access, analyze and use transactional and behavioral data to power highly-targeted customer and prospect communications. The company's hybrid customer-data and marketing-platform model allows companies to grow by fostering direct relationships with customers, without giving up their valuable data to popular big-tech ad platforms. Over 265,000 innovative companies like Unilever, Custom Ink, Living Proof and Huckberry sell more with Klaviyo. Learn more at .

If you are a California, Colorado, Rhode Island, Washington, New York City, or Jersey City resident and this role is a remote role, you can receive additional information about the compensation and benefits for this role, which we will provide upon request. Requests can be submitted here . Additional information regarding benefits can be found at .

      • 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.


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