As a Fullstack Software Engineer II, you will develop RCS and SMS capabilities, architect new services, and improve performance in a collaborative team setting.
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 careers.klaviyo.com to see how we empower creators to own their own destiny.
Why You Should Join the SMS International Team:
This role is for the SMS International team that is part of Mobile Platforms.
The Mobile Platforms team at Klaviyo is responsible for empowering the over 150,000 Ecommerce clients we work with on a global scale to deliver effective experiences on mobile devices. This team focuses on performance optimization and continuous development of our Mobile Marketing Channels (SMS, Push Notifications, In App Messages, WhatsApp and RCS), Mobile SDKs (iOS, Android and React Native). While Email was how Klaviyo began, Mobile messaging is truly the way of the future.
The SMS International team within Mobile Platforms is responsible for the expansion of SMS capabilities into new countries and regions and is also spearheading the development of RCS as a new capability to be offered to customers alongside existing channels. We have an ambitious roadmap for 2025 and 2026 that puts the team at the heart of the company's objectives and it is an exciting time to join the team!
About the Role
As a Fullstack Software Engineer II joining the SMS International team you will be working with a team of 5 other colleagues to deliver RCS and SMS International expansion to meet the company's objectives. You will get the chance to build brand new services, understand how they fit into the bigger picture and plan how to architect and scale them successfully to serve out customers.
What we are looking for
Nice to Have
Technologies we use (not exhaustive):
We use Covey as part of our hiring and / or promotional process. For jobs or candidates in NYC, certain features may qualify it as an AEDT. As part of the evaluation process we provide Covey with job requirements and candidate submitted applications. We began using Covey Scout for Inbound on April 3, 2025.
Please see the independent bias audit report covering our use of Covey here
Our salary range reflects the cost of labour in the country where the job post is advertised. The base salary offered for this position is determined by several factors, including the applicant's job-related skills, relevant experience, education or training, and work location.
In addition to base salary, our total compensation package may include participation in the company's annual cash bonus plan, variable compensation (OTE) for sales and customer success roles, equity, sign-on payments, and a comprehensive range of health, welfare, and wellbeing benefits based on eligibility. Please visit Klaviyo Rewards - Global Benefits to find out more about our Total Rewards package.
Your recruiter can provide more details about the specific salary/OTE range for your preferred location during the hiring process.
Base Pay Range in Local Currency:
£68,000 - £102,000 GBP
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 (@klaviyo.com), instant messaging platforms, or unsolicited calls.
By clicking "Submit Application" you consent to Klaviyo processing your Personal Data in accordance with our Job Applicant Privacy Notice. If you do not wish for Klaviyo to process your Personal Data, please do not submit an application.
Why You Should Join the SMS International Team:
This role is for the SMS International team that is part of Mobile Platforms.
The Mobile Platforms team at Klaviyo is responsible for empowering the over 150,000 Ecommerce clients we work with on a global scale to deliver effective experiences on mobile devices. This team focuses on performance optimization and continuous development of our Mobile Marketing Channels (SMS, Push Notifications, In App Messages, WhatsApp and RCS), Mobile SDKs (iOS, Android and React Native). While Email was how Klaviyo began, Mobile messaging is truly the way of the future.
The SMS International team within Mobile Platforms is responsible for the expansion of SMS capabilities into new countries and regions and is also spearheading the development of RCS as a new capability to be offered to customers alongside existing channels. We have an ambitious roadmap for 2025 and 2026 that puts the team at the heart of the company's objectives and it is an exciting time to join the team!
About the Role
As a Fullstack Software Engineer II joining the SMS International team you will be working with a team of 5 other colleagues to deliver RCS and SMS International expansion to meet the company's objectives. You will get the chance to build brand new services, understand how they fit into the bigger picture and plan how to architect and scale them successfully to serve out customers.
What we are looking for
- 3-5 years of experience in a software engineering discipline
- Experience with full stack application development
- Experience working with both monolithic and microservices architectures
- Experience with database design that can withstand high query volumes
- Experience with CI/CD pipelines
- Experience debugging performance issues and improving application performance
- An interest and aptitude for collaboration across teams and disciplines
Nice to Have
- Experience creating new services with scalability in mind. Exposure to large-scale system design
- Experience with AWS or any similar cloud provider
- Communication domain experience
Technologies we use (not exhaustive):
- Python, Django, Go, React, RabbitMQ, Celery, MySQL, DynamoDB, Elasticache, Redis
- Amazon Web Services (EC2, RDS, Aurora, etc.), Terraform, Kuberentes, Splunk, Buildkite, Grafana, and other modern DevOps tools
We use Covey as part of our hiring and / or promotional process. For jobs or candidates in NYC, certain features may qualify it as an AEDT. As part of the evaluation process we provide Covey with job requirements and candidate submitted applications. We began using Covey Scout for Inbound on April 3, 2025.
Please see the independent bias audit report covering our use of Covey here
Our salary range reflects the cost of labour in the country where the job post is advertised. The base salary offered for this position is determined by several factors, including the applicant's job-related skills, relevant experience, education or training, and work location.
In addition to base salary, our total compensation package may include participation in the company's annual cash bonus plan, variable compensation (OTE) for sales and customer success roles, equity, sign-on payments, and a comprehensive range of health, welfare, and wellbeing benefits based on eligibility. Please visit Klaviyo Rewards - Global Benefits to find out more about our Total Rewards package.
Your recruiter can provide more details about the specific salary/OTE range for your preferred location during the hiring process.
Base Pay Range in Local Currency:
£68,000 - £102,000 GBP
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 (@klaviyo.com), instant messaging platforms, or unsolicited calls.
By clicking "Submit Application" you consent to Klaviyo processing your Personal Data in accordance with our Job Applicant Privacy Notice. If you do not wish for Klaviyo to process your Personal Data, please do not submit an application.
Top Skills
Amazon Web Services
Buildkite
Celery
Django
DynamoDB
Elasticache
Go
Grafana
Kubernetes
MySQL
Python
RabbitMQ
React
Redis
Splunk
Terraform
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If asked to name the birthplace of the RMS Titanic, you might not say Belfast. Similarly, if asked to name Europe's leading destination for foreign direct investment in new software development, Belfast might not come to mind. Yet, both are true. The city has emerged as a tech powerhouse, recently ranked among the best in the U.K. for tech careers — especially for software developers. It also leads the U.K. with the highest percentage of software development jobs advertised.
