Staff Backend Engineer – Calendar Integrations

About HighLevel: HighLevel is an AI powered, all-in-one white-label sales & marketing platform that empowers agencies, entrepreneurs, and businesses to elevate their digital presence and drive growth. We are proud to support a global and growing community of over 2 million businesses, comprised of agencies, consultants, and businesses of all sizes and industries. HighLevel empowers users  with all the tools needed to capture, nurture, and close new leads into repeat customers. As of mid 2025, HighLevel processes over 4 billion API hits and handles more than 2.5 billion message events every day. Our platform manages over 470 terabytes of data distributed across five databases, operates with a network of over 250 microservices, and supports over 1 million hostnames. Our People With over 1,500 team members across 15+ countries, we operate in a global, remote-first environment. We are building more than software; we are building a global community rooted in creativity, collaboration, and impact. We take pride in cultivating a culture where innovation thrives, ideas are celebrated, and people come first, no matter where they call home. Our Impact As of mid 2025, our platform powers over 1.5 billion messages, helps generate over 200 million leads, and facilitates over 20 million conversations for the more than 2 million businesses we serve each month. Behind those numbers are real people growing their companies, connecting with customers, and making their mark - and we get to help make that happen. About the Role: We are building a highly scalable Calendar & Integrations Platform that enables seamless scheduling, real-time event synchronisation, and extensible third-party integrations through a plugin-based architecture. As a Staff Engineer, you will lead the design and evolution of our core sync engine, event models, and integrations runtime - ensuring reliability, consistency, and performance across distributed systems. You will work on complex engineering challenges involving multi-tenant architectures, event standards, large-scale API interactions, recurrence handling, and intelligent sync pipelines. You will also shape the technical direction for our integrations marketplace, mentor engineers, and partner closely with platform, scheduling, AI, and infra teams to build a highly extensible and developer-friendly ecosystem. This role is ideal for someone who has deep experience with distributed systems, standards-based event modeling, multi-provider integrations, or large-scale scheduling infrastructure. Responsibilities:

Architect and evolve a plugin-based integrations marketplace that supports calendars, conferencing tools, CRMs, and productivity apps

Design a high-scale, multi-tenant sync engine for Google, Outlook, Apple Calendar, Zoom, Teams, and other providers

Implement delta sync pipelines using Google Sync Tokens, Microsoft Delta Queries, and CalDAV/WebDAV sync mechanisms

Define and maintain a normalized event model across providers, covering recurrence, attendees, reminders, and conferencing data

Ensure strict standards compliance with iCalendar (RFC 5545), ICS formats, RRULE logic, and timezone rules

Build resilient, idempotent workflows with retries, backoff, dead-letter queues, and replay-safe operations

Create automated sync health scoring and drift detection systems with self-healing and recovery paths.

Develop integration SDKs, OAuth flows, webhooks, and debugging tools to power partner and third-party extension development

Lead architecture reviews, RFCs, and cross-team technical strategy with Scheduling, Platform, AI, Experience, and SDET teams

Mentor engineers and elevate engineering quality through hands-on guidance, design leadership, and best practices

Requirements:

8+ years of backend or platform engineering experience, with 2+ years in a technical leadership role

Deep experience designing integration systems, APIs, SDKs, or plugin architectures

Proven ability to lead cross-functional, platform-level initiatives with strong attention to developer experience

Experience with authentication flows, webhook systems, and sandbox environments for developers

Strong understanding of security, scalability, and extensibility in multi-tenant or developer platform environments

Passion for building tools that enable and empower other developers

Excellent communication skills and the ability to lead a team through ambiguity with clarity

Nice to have:

Experience building marketplaces, developer platforms, or app stores

Familiarity with OAuth2, scoped permissions, event hooks, and audit trails

Exposure to plugin models like Slack apps, Zapier, Shopify apps, or Chrome extensions

Prior experience integrating with calendar or scheduling APIs (Google, Outlook, etc.)