Senior Software Engineer II, Messaging Core in London

At HubSpot, we’re on a mission to help millions of organizations grow better. Our platform is used by businesses worldwide to manage their marketing, sales, service and operations — and under the hood, our product is built to be flexible, secure and empowering for both our customers and our own engineering teams. We believe in autonomy, curiosity and building a workplace where everyone can thrive.

Meet the team: Messaging Core (Messaging Product Group)

The Messaging Product Group builds the apps and infrastructure behind marketing Email, SMS and WhatsApp in HubSpot. We work at a serious scale, powering billions of messages per month. We focus on building reliable systems while continuously innovating the product to help our customers achieve better outcomes.

Messaging Core Backend builds the foundation that every Messaging product depends on. As a Senior Software Engineer II, you’ll build the backend systems that make asset creation, publishing and cross‑product consistency possible, enabling other Messaging teams to ship quickly on top of a reliable, well‑defined platform. You’ll design and evolve distributed systems at scale, tackle complex reliability and data challenges and shape core architecture used across Messaging.

What You’ll Do

• Design and build backend services and APIs for marketing Email, SMS and WhatsApp creation, management and publishing.
• Own and evolve shared infrastructure used across Messaging.
• Lead complex, cross‑team projects (typically 3–6 months) that span multiple services, data stores and product areas.
• Take a data‑driven approach to reliability and performance.
• Contribute to and sometimes lead database and infrastructure initiatives, such as keyspace migrations in partnership with platform teams.
• Debug and resolve production issues across the stack: work with tooling like Metrics, Logfetch, Error Reporting and Tracing and use incident learnings to improve architecture, alerting and runbooks.
• Drive technical design for new features and refactors: write design docs, review peers’ designs and ensure solutions are scalable, maintainable and aligned with the broader Messaging architecture.
• Mentor and level up other engineers on the team via code reviews, pairing and informal coaching, helping them deepen their skills in distributed systems, reliability and product thinking.
• Collaborate closely with frontend, infra and product partners across Messaging and adjacent teams to deliver cohesive, end‑to‑end solutions.
• Participate in on‑call rotations and incident response, contributing to a culture of shared ownership for reliability and sustainable on‑call practices.

What You’ll Bring

• Deep backend engineering experience (typically 5+ years) building and operating production services in a modern microservice environment (e.g. JVM stack, relational databases, event‑driven architectures).
• A track record of leading complex projects (3–6 months) as the primary backend engineer: you’ve owned design, implementation, rollout and long‑term maintenance for systems with real customer and business impact.
• Strong system design skills. You can design and evolve fault‑tolerant, horizontally scalable systems, make pragmatic trade‑offs between short and long‑term needs and keep solutions simple where possible.
• Experience maintaining, implementing and improving service maturity (latency, test coverage, fault tolerance, reliability).
• Comfort working in high‑impact, data‑sensitive systems, including schema changes, migrations and performance‑sensitive paths touching key tables and services in Messaging and Content.
• Excellent collaboration and communication skills across engineering, product and support. Especially when clarifying ownership, triaging issues and aligning on behavior across multiple teams.
• A growth mindset and evidence of multiplicative impact through mentoring others, improving shared libraries or shaping patterns that other teams adopt.

Nice to Have

• Experience in messaging or marketing technology (email/SMS/WhatsApp sending, campaign management, compliance, or analytics).
• Familiarity with MySQL/Vitess and large‑scale data migrations in a sharded environment.
• Background working with CRM objects, properties and usage data, ideally including mirroring content into CRM and managing usage/ownership boundaries.
• Experience with service maturity programs, error budgets and SLO‑driven reliability work within a larger product line.
• Comfort collaborating with frontend teams to design robust contracts and APIs and with infra/platform teams on migrations and tooling improvements.

We know the confidence gap and impostor syndrome can get in the way of meeting spectacular candidates, so please don’t hesitate to apply — we’d love to hear from you.

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