Application Security Engineer

Monzo

🚀 We’re on a mission to make money work for everyone. We’re waving goodbye to the complicated and confusing ways of traditional banking. After starting as a prepaid card, our product offering has grown a lot in the last 10 years in the UK. As well as personal and business bank accounts, we offer joint accounts, accounts for 16-17 year olds, a free kids account and credit cards in the UK, with more exciting things to come beyond. Our UK customers can also save, invest and combine their pensions with us.  With our hot coral cards and get-paid-early feature, combined with financial education on social media and our award winning customer service, we have a long history of creating magical moments for our customers! We’re not about selling products - we want to solve problems and change lives through Monzo ❤️ ----------------------------------------------------------------------------------------------------------------------------------   📍Barcelona, Spain | 💰 Base salary for this role is depending on experience + benefits | Hybrid model: 3 days a week in the office About our Engineering Teams: We have over 400 engineers across Monzo who design and build our in-house banking platform. We have big ambitions for the future, and technology plays a big role in creating a bank our customers want, so engineers at Monzo collaborate across disciplines to solve interesting challenges throughout the company. These range from the products our customers use everyday to underlying infrastructure, security, payments and finance, customer operations, financial crime, and data, to name just a few areas. As a bank, there is scope for impact across a huge number of opportunities. We contribute to open source software as much as possible. Our blog is a good place to learn even more about what we do! What you’ll be working on:  We rely heavily on the following tools and technologies: * Go to write our application code (there’s an excellent interactive Go tutorial here) * Cassandra for most persistent data storage * Kafka for our asynchronous message queue * Envoy Proxy for RPC * Kubernetes and Docker to schedule and run our services  * AWS for most of our infrastructure * React for internal web dashboards * We also have two physical datacenter sites with actual cables to connect to various third parties Your day-to-day    This role is all about collaborating across disciplines to test hypotheses and make a difference to customers. As a product backend engineer you’ll work in a squad alongside product managers, marketers, user researchers, designers, mobile engineers, web engineers, data analysts, business analysts, writers and more!  Together you’ll build and support a particular part of Monzo. Our product squads belong to our wider collectives (a word we use to describe self-governing business units of ~100 people). They are; Money, Borrowing, Fincrime, Customer Operations, Platform, Personal Banking & Business Banking. They’re all looking for additional Backend Engineers right now, we do a standard interview process across all our collectives and at the end we will find the best match for you based on your skills, experience, preferences and aligning with the business need!  Our backend engineers have a variety of different backgrounds. As long as you enjoy learning new things, we’d love to talk to you. We do not ask for formal qualifications or degree requirements for any of our engineering roles. You should apply if: * you have strong experience working on the backend of a technology product * you want to be involved in building a product that you (and the people you know) use every day * you have a product mindset: you care about customer outcomes and you want to make data-informed decisions * you’re comfortable working in a team that deals with ambiguity * you’re interested in distributed systems and writing resilient software * you have some experience with strongly-typed languages (Go, Java, C, Scala etc.). * you think you’d enjoy the kind of work we’re doing We're on the look out for L60 Engineers at the moment, you can read more in our Engineering Progression Framework we are also hiring on L40 & L50, our interview process will determine your levelling.  The Interview Process: Our interview process involves three main stages:  1. Initial Call  2. Take home task or pair coding exercise  3. Final interview including a system design and a behavioural interview  One of our engineers has written a detailed blog on their experience through this process, for extra details, hints and tips please see here. What’s in it for you: 💰Base salary range for this role is depending on experience + equity + stock options & benefits  📍Barcelona, Spain ⏰ We offer flexible working hours and trust you to work enough hours to do your job well, at times that suit you and your team. 📚Learning budget of €1,200 a year for books, training courses and conferences #LI-JS1 ---------------------------------------------------------------------------------------------------------------------------------- Equal opportunities for everyone Diversity and inclusion are a priority for us and we’re making sure we have lots of support for all of our people to grow at Monzo. At Monzo, we’re embracing diversity by fostering an inclusive environment for all people to do the best work of their lives with us. This is integral to our mission of making money work for everyone. You can read more in our blog, 2026 Diversity and Inclusion Report and 2025 Gender Pay Gap Report. We’re an equal opportunity employer. All applicants will be considered for employment without attention to age, ethnicity, religion, sex, sexual orientation, gender identity, family or parental status, national origin, or veteran, neurodiversity or disability status. If you have a preferred name, please use it to apply. We don't need full or birth names at application stage 😊

Monzo

🚀 We’re on a mission to make money work for everyone. We’re waving goodbye to the complicated and confusing ways of traditional banking. After starting as a prepaid card, our product offering has grown a lot in the last 10 years in the UK. As well as personal and business bank accounts, we offer joint accounts, accounts for 16-17 year olds, a free kids account and credit cards in the UK, with more exciting things to come beyond. Our UK customers can also save, invest and combine their pensions with us.  With our hot coral cards and get-paid-early feature, combined with financial education on social media and our award winning customer service, we have a long history of creating magical moments for our customers! We’re not about selling products - we want to solve problems and change lives through Monzo ❤️ ----------------------------------------------------------------------------------------------------------------------------------   📍Barcelona, Spain | 💰 Base salary for this role is depending on experience + Incentive Awards tied to your performance  + benefits  Hybrid model: 3 days a week in the office About our Engineering Teams: We have over 400 engineers across Monzo who design and build our in-house banking platform. We have big ambitions for the future, and technology plays a big role in creating a bank our customers want, so engineers at Monzo collaborate across disciplines to solve interesting challenges throughout the company. These range from the products our customers use everyday to underlying infrastructure, security, payments and finance, customer operations, financial crime, and data, to name just a few areas. As a bank, there is scope for impact across a huge number of opportunities. We contribute to open source software as much as possible. Our blog is a good place to learn even more about what we do! Your day-to-day    This role is all about collaborating with your team to make a difference to your customers. As a backend engineer you’ll work in a squad alongside other disciplines like product managers, marketers, user researchers, designers, mobile engineers, web engineers, data analysts, business analysts, writers and more!  Together you’ll build and support a particular part of Monzo. Our squads belong to our wider collectives (a word we use to describe self-governing business units of ~100 people). They are; Core Banking, Business Banking, Wealth, Borrowing, Growth, Payments, Platform, Fincrime, Security & Expansion. They’re all looking for additional Backend Engineers right now, we do a standard interview process across all our collectives and at the end we will find the best match for you based on your skills, experience, preferences and aligning with the business need!  Our backend engineers have a variety of different backgrounds. As long as you enjoy learning new things, we’d love to talk to you. We do not ask for formal qualifications or degree requirements for any of our engineering roles. You should apply if: * you have strong experience working on the backend of a technology product * you want to be involved in building a product that you (and the people you know) use every day * you have a product mindset: you care about customer outcomes and you want to make data-informed decisions * you’re comfortable working in a team that deals with ambiguity * you’re interested in distributed systems and writing resilient software * you have some experience with strongly-typed languages (Go, Java, C, Scala etc.). * you think you’d enjoy the kind of work we’re doing We're on the look out for L50 Engineers at the moment, you can read more in our Engineering Progression Framework - we will interview you across the whole frame work, so if you are not sure what level you are aiming for please chat to your recruiters!  Not ticking every box? That’s totally okay! Studies show that women and people of colour might hesitate to apply unless they meet every single requirement. At Monzo, we’re dedicated to creating a diverse and welcoming team. If you’re passionate about this role and keen to learn and grow with us, we encourage you to apply— even if you don’t have everything thats listed just yet. Drop us your application, we’d love to hear from you! What you’ll be working on:  We hire very technically agnostic so whilst we use the below technologies we do not expect prior knowledge, you will be fully supported in our organised onboarding to get up to speed in the below:  * Go to write our application code (there’s an excellent interactive Go tutorial here) * Cassandra for most persistent data storage * Kafka for our asynchronous message queue * Kubernetes and Docker to schedule and run our services  * Envoy Proxy for RPC * AWS for most of our production infrastructure and GCP for most of our data infrastructure * React for our public web apps and internal tools * We also have physical datacenters with actual cables to connect to various third parties The Interview Process: Our interview process involves three main stages:  1. Initial Call  2. Take home task or pair coding exercise  3. Final interview: including a system design and a behavioural interview  Our average process takes around 4 weeks but we will always work around your availability.  One of our engineers has written a detailed blog on their experience through this process, for extra details, hints and tips please see here. What’s in it for you: 💰 Base salary for this role is depending on experience + Incentive Awards tied to your performance  + benefits  📍Barcelona, Spain ⏰ We offer flexible working hours and trust you to work enough hours to do your job well, at times that suit you and your team. 📚Learning budget of €1,200 a year for books, training courses and conferences   #LI-JS1 ---------------------------------------------------------------------------------------------------------------------------------- Equal opportunities for everyone Diversity and inclusion are a priority for us and we’re making sure we have lots of support for all of our people to grow at Monzo. At Monzo, we’re embracing diversity by fostering an inclusive environment for all people to do the best work of their lives with us. This is integral to our mission of making money work for everyone. You can read more in our blog, 2026 Diversity and Inclusion Report and 2025 Gender Pay Gap Report. We’re an equal opportunity employer. All applicants will be considered for employment without attention to age, ethnicity, religion, sex, sexual orientation, gender identity, family or parental status, national origin, or veteran, neurodiversity or disability status. If you have a preferred name, please use it to apply. We don't need full or birth names at application stage 😊

Proton

About Proton  Join Proton and build a better internet where privacy is the default Proton was founded in 2014 by scientists from CERN on a simple truth: privacy is a fundamental human right. Since then, we’ve built the world’s largest encrypted email service (Proton Mail) and expanded into Proton VPN, Proton Drive, Proton Pass, and Proton Calendar—tools used by millions globally to protect their freedom, fight censorship, and keep their data safe. In some situations, Proton has literally helped save lives! We are profitable, independent (no VC control), and selectively hire from the top ~1% of applicants. Our 500+ team members across 50+ countries come from leading organizations and elite academic backgrounds. We move fast, keep hierarchy light, and prioritize impact over optics. If you want to do meaningful work with exceptionally high-caliber people, this is it. Join us and do work you can truly be proud of. Check our open-source projects here! The Role Based in our Barcelona office, you’ll join one of several high-impact product teams across Proton Pass, Proton Wallet/Payments, and Proton VPN, helping build privacy-first products used by millions around the world. From secure password management and identity protection to encrypted financial tools and internet freedom products that help users bypass censorship and surveillance, you’ll work on technically ambitious products with real-world impact. As a senior engineer, you’ll collaborate closely with product, design, and engineers across Proton to build and ship high-quality experiences on Apple platforms, helping define what “great” looks like for privacy-focused consumer products at scale. What we are looking for * You have extensive experience building and shipping high-quality iOS applications * You care deeply about product quality, usability, and delivering exceptional user experiences * You have strong experience building maintainable, scalable, and testable mobile architectures * You are comfortable working across large codebases and collaborating across multiple teams * You have experience mentoring engineers and raising the technical bar within a team * You have a strong understanding of performance, concurrency, and mobile memory management * You are comfortable navigating ambiguity and contributing to product and technical discussions * Experience with privacy, security, encryption, sync systems, or offline-first architectures is a strong plus * Rust experience is a plus, but not required as we continue moving towards a platform-independent Rust logical core communicating with the iOS application via generic interfaces What We Offer * Work that Matters: millions of people trust Proton with their privacy. We answer only to our users — not advertisers, not investors with conflicting agendas, not governments. The work you do here is real, and the impact is measurable. (read more about our impact here) * Stock Options: at Proton, we all have the opportunity to be owners of the company. From day one, you have a real stake in what we're building. When Proton wins, you win. * Technology: you'll get the right hardware and the right software you need to do your best work. * Learning & Development: we invest in your growth because sharp people make us better. Proton is one of the fastest ways to accelerate your career because you'll be thrown into real challenges, with real ownership, from day one. * Employee Benefits: your wellbeing isn't an afterthought. We offer strong health coverage, solid retirement options, generous leave, and wellness support so you can bring your best self to work every day * In-Person Collaboration: Amazing things happen when passionate, smart, and purposeful people get together in the same room. With offices across Geneva, Zürich, Barcelona, London and more, you'll spend most of your time collaborating face-to-face with people who genuinely care about what they're building * Food: Lunch and snacks are on us every day in our offices so you can focus on the work and not on what's for lunch. * Transport: getting to the office shouldn't cost you. We cover public transport, bike allowances, or parking, whichever works for you. * Flexible Working: you own your schedule. Set hours that work for you and your team — because outcomes matter more than when the clock says you started.