Principal Full-Stack Engineer

Job Description: Principal Full-Stack Engineer

Role Overview

We are looking for a Principal Full-Stack Engineer to set the technical direction for Mozark ’ s AI-native Digital Experience Testing Platform. This is a hands-on technical leadership role. As a Principal, you will own architecture across product lines, drive engineering excellence, partner directly with Product Management, DevSecOps, and the Agentic AI team, and be a force multiplier across the engineering organisation. You will write production code, lead the hardest technical problems, and shape how Mozark builds - for quality, security, scale, and AI at the core.

Key Responsibilities

• Set and evolve the architecture for full-stack systems across product lines

• Drive cross-cutting technical initiatives - performance, scalability, high availability (5-9s targets), observability, and auto-remediation.

• Lead complex full-stack delivery: design and build services in Python (FastAPI), front-ends in React/React Native, real-time pipelines (WebRTC, streaming), and data platforms

• Establish secure-by-design patterns in collaboration with DevSecOps - threat modelling, secrets management, dependency hygiene, runtime hardening, and supply-chain security.

• Raise the bar on quality - define and enforce SDLC quality gates, code review standards, automated testing strategy (Playwright, k6), and release engineering practices.

• Lead architectural reviews, RFCs, and design documents; act as a final technical reviewer for high-impact changes.

• Mentor and coach Senior and Staff engineers across product lines; develop the next generation of technical leaders.

• Eliminate single points of failure across SRE and product-critical components through technical design and knowledge distribution.

• Represent engineering in customer, regulator, and partner conversations when deep technical depth is required.

What We ’ re Looking For

• 12+ years of professional software engineering experience, with a meaningful portion spent designing and operating large-scale production systems.

• Track record of leading architecture across multiple services or product lines, with measurable impact on scale, reliability, security, or cost.

• Deep, hands-on expertise across the full stack - strong backend (Python/Go/Java + FastAPI or equivalent), proficient front-end (React, React Native, or equivalent), and fluent with cloud-native infrastructure (Docker, Kubernetes).

• Strong systems fundamentals - distributed systems, concurrency, storage engines, networking, security, and performance engineering.

• Deep experience with AWS and/or GCP, including identity, networking, multi-region deployment, data residency, and cost optimisation.

• Demonstrated experience designing multi-tenant SaaS platforms, including IAM, isolation, metering, and observability.

• Experience integrating LLMs or agentic workflows into production products - managing prompt design, evaluation, guardrails, latency, and cost.

• Strong understanding of secure SDLC, DevSecOps, and compliance-driven engineering

• Excellent written and verbal communication - able to write crisp design documents, lead architecture reviews, and explain trade-offs to executive and customer audiences.

• Proven ability to mentor senior engineers, influence without authority, and lead through technical credibility.

• Nice to have: device-cloud or mobile automation infrastructure, WebRTC/real-time media, geospatial systems (H3), test orchestration platforms, or RUM/observability platforms.

Why Join Us?

• Shape the architecture of a category-defining AI-native Digital Experience Testing Platform serving customers across 20+ countries in Telco, BFSI, OTT, and Public Sector.

• Direct partnership with the CTO, CPO, and co-CEOs; high-visibility role with influence on product, technology, and go-to-market decisions.

• Work at the intersection of agentic AI, device-cloud infrastructure, network truth engines .

. Skillset Required: Full-stack development, Python, FastAPI, React, React Native, WebRTC, streaming, data platforms, secure-by-design patterns, threat modelling, secrets management, dependency hygiene, runtime hardening, supply-chain security, SDLC quality gates, code review standards, automated testing strategy, Playwright, k6, release engineering practices, architectural reviews, RFCs, design documents, mentoring, coaching, distributed systems, concurrency, storage engines, networking, security, performance engineering, AWS, GCP, cloud-native infrastructure, Docker, Kubernetes, multi-tenant SaaS platforms, IAM, isolation, metering, observability, LLM integration, agentic workflows, prompt design, evaluation, guardrails, latency management, cost optimisation, secure SDLC, DevSecOps, compliance-driven engineering, written communication, verbal communication, technical leadership, device-cloud automation, mobile automation infrastructure, geospatial systems, test orchestration platforms, RUM, observability platforms