Senior Infrastructure Engineer

About Keystone AI & CallMiner Keystone AI is a conversational AI company originally founded in Central Europe, focused on building advanced voice and automation solutions for customer communication. In May 2025, Keystone AI was acquired by CallMiner, a global leader in AI-powered conversation intelligence. While we are now part of the CallMiner group, Keystone AI continues to operate as an independent, growing entity with its own product, engineering team, and culture. The acquisition allows us to combine the agility and innovation of a startup with the stability, scale, and global reach of an established SaaS leader. Job Summary As part of the CallMiner Engineering and Operations Team, the DevOps System Administrator is responsible for the reliability, security, and performance of the infrastructure that delivers CallMiner's intelligent CX automation solutions to enterprise customers, including OmniAgent. The primary focus of this role is managing and supporting customer-facing infrastructure: deploying, operating, and troubleshooting the systems that connect AI virtual agents to customers' contact center and telephony environments. A central part of this responsibility is SIP telephony integration – owning the end-to-end technical path from the moment a customer's phone rings to the moment the AI agent answers, across SIP trunks, carriers, PBX systems, session border controllers, and enterprise networks. The DevOps System Administrator partners closely with Engineering, Delivery, and Customer Success teams to support customer deployments, resolve infrastructure and connectivity issues, plan capacity, and ensure the availability of real-time, voice-first services handling millions of customer interactions annually. The ideal candidate is a proactive problem-solver who thrives on ownership and operational excellence in a fast-paced environment. This position is based in Prague, Czech Republic, and supports CallMiner's Intelligent CX Automation platform serving customers throughout Europe and globally. Responsibilities Administer, monitor, and maintain customer-facing cloud infrastructure (Azure and/or AWS, OVH Cloud) supporting CallMiner's intelligent CX automation platform Own SIP telephony integrations for customer deployments: configure and maintain connectivity via SIP trunking providers, direct trunks, and customers' enterprise telephony infrastructure (PBX, SBC, CCaaS platforms) Design reliable call paths balancing latency, audio quality, reliability, and security constraints Diagnose and resolve complex telephony and connectivity issues across customer environments, including call routing, NAT traversal, codec compatibility, RTP/audio quality, firewall and QoS configuration Ensure high availability, low latency, and resilience of real-time voice and conversational AI services Support customer onboarding and go-lives in coordination with Delivery and Professional Services teams, from proof-of-concept through production Manage containerized workloads and orchestration platforms (Docker, Kubernetes) Lead incident response and root cause analysis for infrastructure, telephony, and connectivity issues Perform routine system administration tasks including patching, backups, disaster recovery testing, user and access management, and capacity planning Harden systems and enforce security best practices, supporting compliance requirements (e.g., ISO 27001, GDPR, SOC 2) and audit activities Manage databases, networking, DNS, load balancing, certificates, and VPN/firewall configurations Collaborate with Engineering teams to translate recurring customer integration challenges into platform and process improvements Create and maintain clear technical documentation, runbooks, and integration guides for customer-facing infrastructure Requirements 5+ years of experience in System Administration, DevOps, VoIP/telephony engineering, or related infrastructure roles Bachelor's degree preferred in Computer Science, Information Technology, or related discipline, or equivalent practical experience Hands-on experience with SIP-based integrations, SIP trunking, call routing concepts, and real-world troubleshooting across networks and enterprise environments Strong Linux administration skills (Ubuntu/Debian/CentOS), including shell scripting (Bash) and scripting in Python or similar Hands-on experience with public cloud platforms (Azure and/or AWS), including compute, networking, storage, and identity services Practical experience with containerization (Docker) and orchestration (Kubernetes) Experience with monitoring, logging, and alerting tools and a structured approach to incident management Solid understanding of networking fundamentals (TCP/IP, DNS, VPN, firewalls, load balancing, NAT) and security best practices Strong troubleshooting and problem-solving skills with a proactive, ownership-driven mindset and direct customer impact Strong organizational skills, managing multiple priorities independently in a fast-paced, customer-facing en