Senior Telco Operations Engineer (VoIP/SMS)

Rakuten Viber is one of the most popular and downloaded apps in the world. Working with us provides a unique opportunity to influence hundreds of millions of our users and to be part of the journey that makes us a super-app. Our mission is to make people’s lives easier by enabling meaningful connections, from precious moments with family and friends, through managing business relationships to pursuing their passions. 

We are seeking an experienced Senior VoIP/SMS Engineer to join our Telco Operations team. The team manages Viber's voice and messaging infrastructure at scale, including wholesale voice and SMS operations, user activation services, and anti-fraud systems. This role combines hands-on engineering with operational leadership, working across carrier partners, internal platforms, and cross-functional teams to ensure service quality and business continuity.

• Take a tech-lead role within the team: coordinate engineering tasks, guide junior members, own escalation decisions, and represent the team in partner-facing communication
• Operate and maintain large-scale VoIP and SMS platforms in a cloud environment, ensuring high availability and optimal performance
• Provide Level II and Level III technical support for voice and messaging services, handling complex escalations from partners and internal teams
• Onboard new carrier partners: configure trunks, accounts, and routing for voice and SMS wholesale operations
• Investigate and resolve communication issues across the network: call quality, SMS delivery failures, routing anomalies, and protocol-level bugs
• Drive internal infrastructure projects: platform upgrades, legacy system decommissioning, CDR integration, and process automation
• Monitor, test, and evaluate network systems; recommend improvements to maintain or expand service levels
• Collaborate with Commercial, Routing, and Back-End teams to implement required platform changes
• Contribute to process improvements and automation of operational workflows
• Participate in anti-fraud and anti-spam efforts for Voice/SMS services, including traffic pattern analysis.

• 3+ years of hands-on experience in VoIP/SMS operations or telecom engineering
• Strong knowledge of SIP protocol, SMPP/HTTP messaging, and voice routing (Class 4/5 switches)
• Experience with network debugging tools: Wireshark, tcpdump, SIP trace analysis
• Solid understanding of TCP/IP, networking fundamentals (switches, firewalls, routers, LAN/WAN/VPN)
• Experience with carrier interconnections: trunk setup, capacity management, and partner onboarding
• Familiarity with voice/SMS billing and rating systems
• Proven ability to work in a ticket-driven support environment with SLA awareness
• Excellent written and verbal communication skills in English
• Strong interpersonal skills, able to communicate effectively with carriers, internal stakeholders, and cross-functional teams.

• Experience with open-source or commercial VoIP platforms (OpenSIPs, FreeSWITCH, MVTS, Oracle SBC, etc.)
• Proficiency in scripting languages (Python, Bash, Lua)
• Experience with AWS or other cloud environments
• Linux system administration experience
• Familiarity with WebRTC
• Experience with ticketing and workflow systems (Zendesk, JIRA)
• Background in telecom fraud detection or traffic analysis
• Experience leading or mentoring junior engineers
• Working knowledge of REST APIs and integration workflows.