# Work & Case Studies — Mohammad Shadikur Rahman > Comprehensive portfolio of cloud infrastructure automation, telecommunications platform engineering, and full-stack applications built by Mohammad Shadikur Rahman. --- ## FusionPBX automation (VoIP SaaS & Automation) - **Page URL**: https://shadikur.com/work/fusionpbx-automation - **Markdown Text URL**: https://shadikur.com/work/fusionpbx-automation.txt - **Role**: Platform owner · Architecture, backend automation & operations (2020 — ongoing) - **Tech Stack**: FreeSWITCH, FusionPBX, PHP, PostgreSQL, Azure Functions, SIP, Automation - **Repository**: https://github.com/shadikur/fusionpbx - **Live Demo / Write-up**: https://office.pbx.shadikur.com/ - **Overview**: A production multi-tenant communications platform that automates PBX provisioning, backups, and health monitoring—turning repeatable telecom operations into a scalable service. ### Problem Statement Provisioning and operating customer PBX environments manually creates inconsistent configurations, slow onboarding, and avoidable operational risk. My earlier work across 200+ FreePBX and FusionPBX deployments showed exactly where these repetitive processes fail at scale. ### Technical Approach & Solution I designed a multi-tenant platform on FusionPBX and FreeSWITCH, using PHP and PostgreSQL for tenant-aware application logic. Azure Functions handle scheduled and event-driven workflows including tenant provisioning, nightly backups, and proactive health checks. The design separates telephony, data, and automation concerns so each can be maintained safely. ### Key Results & Impact The platform remains in active operation and continues to evolve. It demonstrates end-to-end ownership across SIP infrastructure, backend development, database design, cloud automation, observability, backup strategy, and production support—while reducing the manual effort and inconsistency involved in managing multiple customer environments. --- ## Local LLM, Voice Agent & AI Infrastructure Lab (AI Infrastructure & Voice Systems) - **Page URL**: https://shadikur.com/work/local-llm-voice-agent-ai-infrastructure-lab - **Markdown Text URL**: https://shadikur.com/work/local-llm-voice-agent-ai-infrastructure-lab.txt - **Role**: AI infrastructure engineer · Architecture, integration & operations (2026 — ongoing) - **Tech Stack**: Local LLMs, AI Agents, Whisper, LiveKit, Docker, GPU Inference, Speech Recognition, Voice Agents - **Repository**: #private-repo - **Live Demo / Write-up**: - **Overview**: A hands-on AI infrastructure lab for private local language models, real-time conversational voice agents, GPU-accelerated speech recognition and reliable workflow automation. ### Problem Statement Practical conversational AI systems must balance privacy, response latency, speech quality, hardware constraints and operational reliability across several tightly coupled services. ### Technical Approach & Solution I designed and operated a containerized lab integrating local large language models, GPU-accelerated Whisper speech recognition, LiveKit real-time communications, voice-agent orchestration and supporting automation. The work includes model and hardware evaluation, service integration, latency tuning, monitoring and deployment workflows. ### Key Results & Impact The lab provides a working environment for experimenting with private AI assistants and real-time voice systems while demonstrating end-to-end capability across GPU infrastructure, speech pipelines, container operations, observability and production-minded AI integration. --- ## Teams ↔ OpenSIPS SBC (Enterprise Communications Integration) - **Page URL**: https://shadikur.com/work/teams-opensips-sbc - **Markdown Text URL**: https://shadikur.com/work/teams-opensips-sbc.txt - **Role**: Solution architect & implementation engineer (Enterprise deployment) - **Tech Stack**: Microsoft Teams, OpenSIPS, SIP, RTPProxy, Linux, Direct Routing - **Repository**: https://github.com/shadikur/opensips - **Live Demo / Write-up**: https://github.com/shadikur/opensips - **Overview**: A custom session border controller connecting Microsoft Teams Direct Routing with existing SIP infrastructure, providing controlled signaling, media routing, and interoperability. ### Problem Statement The organization needed Microsoft Teams calling to interoperate reliably with its existing SIP trunks and telephony environment without replacing established carrier and PBX infrastructure. ### Technical Approach & Solution I designed and deployed an OpenSIPS-based SBC for SIP signaling and used RTPProxy for media handling. I implemented routing and interoperability logic, connected Teams Direct Routing to the on-premises voice environment, and applied operational controls for maintainability and troubleshooting. ### Key Results & Impact The integration enabled Teams users to use the existing telephony infrastructure through a purpose-built, supportable bridge. It showcases practical expertise across Microsoft cloud telephony, SIP routing, Linux networking, media paths, production diagnostics, and enterprise system integration. --- ## Proxmox installer (Infrastructure Automation) - **Page URL**: https://shadikur.com/work/proxmox-installer - **Markdown Text URL**: https://shadikur.com/work/proxmox-installer.txt - **Role**: Creator & maintainer (Ongoing open-source project) - **Tech Stack**: Proxmox VE, Debian 12/13, Shell, Linux, Virtualization, Automation - **Repository**: https://github.com/shadikur/proxmox/tree/master - **Live Demo / Write-up**: https://github.com/shadikur/proxmox/tree/master - **Overview**: A repeatable bare-metal provisioning workflow that converts a minimal Debian server into a ready-to-manage Proxmox VE hypervisor with a single command. ### Problem Statement Manual hypervisor installation is repetitive and easy to perform inconsistently, especially when rebuilding hosts or preparing multiple lab and server environments across different Debian releases. ### Technical Approach & Solution I built a shell-based installer that detects Debian 12 or 13, selects the compatible Proxmox VE release, configures the required repositories and packages, and produces a consistent web-manageable host. The workflow is documented for use on dedicated servers and virtualization-capable VPS environments. ### Key Results & Impact The project reduces a multi-step infrastructure setup to a repeatable command and supports both Proxmox VE 8.x and 9.x installation paths. It demonstrates Linux administration, defensive automation, release compatibility, documentation, and infrastructure reproducibility. --- ## Leben in Deutschland App (lebentest.de) (Civic Education Platform) - **Page URL**: https://shadikur.com/work/leben-in-deutschland-app-lebentest-de - **Markdown Text URL**: https://shadikur.com/work/leben-in-deutschland-app-lebentest-de.txt - **Role**: Full-stack product engineer (2025 — ongoing) - **Tech Stack**: Next.js, React, Express, MongoDB, Clerk, Node.js, Authentication - **Repository**: #private_repo - **Live Demo / Write-up**: https://lebentest.de - **Overview**: A full-stack learning platform that helps people prepare for Germany’s Leben in Deutschland citizenship test through an accessible, structured online experience. ### Problem Statement People preparing for Germany’s citizenship test need a straightforward way to study and practise the official subject matter without navigating fragmented resources or complicated learning systems. ### Technical Approach & Solution I developed the product across the frontend, backend, data layer, and authentication flow. Next.js delivers the user experience, Express handles application services, MongoDB stores platform data, and Clerk provides managed identity and secure account access. ### Key Results & Impact The result is a live, end-to-end education product that turns a real user need into an accessible web application. It demonstrates product thinking alongside full-stack delivery, authenticated user journeys, API design, data modelling, deployment, and ongoing ownership. --- ## Direct Links & Resources - **Portfolio Overview**: https://shadikur.com - **Career History**: https://shadikur.com/experience.txt - **Technical Articles**: https://shadikur.com/blog.txt - **LLM Full Index**: https://shadikur.com/llms-full.txt