Senior Software Engineer

About the role

Five9 is a leading provider of cloud contact center software, and we're looking for a Senior Software Engineer to join our team. This is a hands-on developer role focused on transforming our internal platform tooling and driving full-stack engineering maturity.

Responsibilities

• Rapidly audit and refactor existing internal tools and services to strictly comply with 12-factor application principles.
• Own end-to-end delivery of modernized services: back-end APIs (Go/Python) paired with clean, functional front-end interfaces (React or Vue).
• Decompose monolithic or ad-hoc scripts into properly structured, independently deployable services with clearly defined interfaces.
• Build and maintain internal web UIs using modern front-end frameworks (React or Vue).
• Design and develop robust REST/gRPC back-end APIs in Go and Python following clean architecture patterns.
• Ensure front-end and back-end components are instrumented end-to-end with traces, metrics, and structured logs from day one.
• Own the platform observability stack: design, implement, and continuously improve our Grafana, Prometheus, and Loki deployment for all internal services.
• Define and enforce instrumentation standards - every new or refactored service must ship with meaningful RED metrics, structured JSON logs forwarded to Loki, and distributed traces.
• Drive log aggregation strategy with Loki - label taxonomy, retention policies, and LogQL query libraries for common operational queries.
• Drive the modernization of legacy platform components with a bias toward simplicity and operational transparency.
• Lead the refactoring of existing deployment pipelines to be fully Kubernetes-native.
• Establish automated testing gates (unit, integration, contract) as hard requirements in the pipeline.
• Technical Leadership & Mentorship: Mentor mid-tier developers, establish coding standards, enforce peer reviews, and reduce technical debt.
• Maintain and overhaul technical documentation; make it easy for new engineers to onboard and contribute.
• Drive enterprise-grade infrastructure automation and orchestration using Ansible, AWX, and Terraform.
• Oversee the secure and highly available architecture of core lifecycle services such as Harbor and GitLab.

Qualifications

• 8+ years of software engineering with proven technical leadership and architectural design experience.
• Full-Stack Development: Strong front-end skills (React or Vue) alongside deep back-end experience - you are comfortable owning the full request lifecycle from UI click to database.
• Observability Expertise: Deep, hands-on expertise with Grafana, Prometheus, and Loki - not just deploying them, but designing dashboards, writing PromQL/LogQL, building exporters, and enforcing instrumentation standards across a team.
• 12-Factor Mastery: Demonstrated experience auditing and refactoring real applications to be 12-factor compliant in a production environment.
• Programming: Deep expertise in Python and Go (Golang) for building distributed systems and enterprise APIs.
• Kubernetes Certification: CKA or CKAD strictly required (CNCF).
• Hands-on experience with on-premise clusters, preferably Rancher.
• Cloud & Infrastructure: Strong experience with OpenStack, private cloud environments, and foundational infrastructure networking.
• Automation & Tooling: Extensive experience with Ansible, AWX/Tower, Harbor, and GitLab.
• Modern Delivery: Proven expertise in SDLC practices, code refactoring, automated testing, and GitOps (ArgoCD).