Customer Success Manager

Harmonic Security; Greater London; Hybrid; GBP 70,000 - 90,000; Full time

Job summary

A cybersecurity innovator in Greater London is seeking a Customer Success Manager to manage the entire customer lifecycle, ensuring measurable adoption and retention. The ideal candidate will have over 7 years of experience in customer success or account management, showcasing exceptional communication and analytical skills. Benefits include competitive pay, comprehensive perks, and a chance to shape company culture as the team redefines cybersecurity.

Benefits

Competitive pay

Pension plan

Generous PTO

Flexible hybrid work

Qualifications

• 7+ years in customer success or related client-facing role.
• Experience with success programs demonstrating ROI.
• Strong understanding of success metrics (NRR, GRR, CSAT).

Responsibilities

• Manage the full customer lifecycle from onboarding to renewal.
• Conduct Quarterly Business Reviews for key accounts.
• Develop data-driven insights for business outcomes.

Skills

Customer success

Account management

Analytical skills

Exceptional communication

Organization

Tools

CRM tools

Job description

About Harmonic

Harmonic Security lets teams adopt AI tools safely by protecting sensitive data in real time with minimal effort. It gives enterprises full control and stops leaks so that their teams can innovate confidently.

We are led by cybersecurity experts and backed by top investors including N47, Ten Eleven Ventures, and In-Q-Tel.

As we expand rapidly across the U.S. and Europe, we’re looking for a Customer Success leader who can help us deliver an exceptional experience to every customer. You’ll play a foundational role in shaping how Harmonic drives adoption, retention, and long‑term value as we scale. This is a chance to join early, influence our customer journey end‑to‑end, and help define what great looks like in a new category.

About the Team

Our Customer Success team delivers a world‑class experience for every customer. We don’t believe in one‑size‑fits‑all — instead, we take a partnership approach to help our customers realize their vision and achieve meaningful business outcomes through Harmonic Protect.

About the Role

As a Customer Success Manager, you’ll own the full customer lifecycle — from onboarding to renewal — and ensure our customers achieve measurable adoption, retention, and ROI. You’ll be a trusted advisor to executives and technical stakeholders alike, building relationships that drive long‑term success.

What You’ll Do

• Serve as the primary point of contact for key accounts, adapting to evolving customer needs.
• Own the end‑to‑end customer lifecycle, from onboarding to renewal.
• Lead Quarterly Business Reviews (QBRs) and executive‑level engagements.
• Develop and present data‑driven insights that connect product usage to business outcomes.
• Champion the voice of the customer, ensuring their needs shape our product and strategy.
• Collaborate closely with Customer Success leadership to help build, refine, and scale the Customer Success organization — contributing to the playbooks, processes and metrics that define how Harmonic delivers value to customers at scale.

What You Bring

• 7+ years in customer success, account management, or a related client‑facing role.
• Experience building and executing success programs that demonstrate ROI.
• Strong analytical skills with an understanding of success metrics (NRR, GRR, CSAT, time‑to‑value).
• Exceptional communication and presentation skills with executive stakeholders.
• Highly organized, adaptable, and proactive — you raise your hand, take initiative, and go the extra mile.
• Comfort with technical concepts and ability to translate them into customer value.
• Familiarity with CRM and customer success tools.
• (Bonus) Experience in cybersecurity or similar technology industries.

What Success Looks Like

• Customers are realizing measurable ROI and expanding their usage of Harmonic.
• Renewals and retention metrics are strong, with clear adoption milestones hit.
• QBRs drive executive alignment and confirm Harmonic as a trusted partner.
• Customer insights are shaping our product roadmap and go‑to‑market strategy.

Why Join Us

This isn’t just a job; it’s an opportunity to be part of a team that’s redefining cybersecurity. At Harmonic, we believe today’s talent is tomorrow’s success — and we’re committed to creating an environment where you can do your best work.

• Competitive pay and meaningful equity with direct impact in Harmonic’s success.
• Comprehensive benefits, pension plan, generous PTO, and flexible hybrid work.
• A small, passionate team that values transparency, creativity, and learning.
• Thoughtful leadership that cares deeply about growth, impact, and people.
• Annual global offsites (past trips include Lisbon and Nashville).
• The chance to shape both our product and our culture as we build a category‑defining company.

Harmonic’s Core Values

• Flourish in the Unknown: Thrive in unfamiliar situations that require initiative and rapid decision‑making.
• Never Full: Stay hungry for opportunities to learn, grow, and do more.
• Perfect Harmony: Create cohesion through collaboration, feedback, and shared success.