CV
Cesar Petrescu · Founder, PhotonSpark · Infrastructure & Network Engineer
Focus and availability
SRE, Systems, DevOps and Networking roles, with a focus on reliable infrastructure, automation and observability.
Remote preferred during university. Onsite only in Bucharest; unavailable for hybrid work or relocation to other cities during the academic year.
Experience
System Administrator, RADIOCOM
Deployed a nationwide VPLS network for a major client - multi-site Layer 2 connectivity with high availability across all locations. Built and shipped an internal operations platform (CRM, ticketing, contracts) now used daily by NOC and Call Center teams, replacing spreadsheet-based workflows. Operate Linux and Windows servers with automated backups and Cisco network infrastructure.
- Developed RADI, an internal RAG assistant over company procedures, work instructions and regulations, with multi-hop retrieval, reranking and a final source check.
CTO & Founder, PhotonSpark
Manage PhotonSpark’s websites and infrastructure end to end: distributed mail, Kubernetes web hosting, shared Ceph storage and self-hosted AI services.
- Designed and operate a 25-OSD Ceph cluster with 256 TiB raw capacity, three-way replication, RBD and CephFS, backing two Proxmox VE clusters and a 15+ server fleet.
- Support AS216249 alongside the company’s network engineer: a company-owned /24 IPv4 block announced over upstream eBGP, with standby DDoS mitigation sessions.
- Built a Go operations orchestrator with event-sourced state, policy decisions and an append-only audit log.
Infrastructure & Network Consultant, Freelance client engagements
Deliver infrastructure, networking and applied AI work for client environments.
- Radburg: tire-sidewall recognition with OCR, a self-hosted vision-language model, deterministic validation and field-level provenance.
- Leclinic: manage the UniFi network and a WireGuard site-to-site connection to a software vendor.
- Radburg: migrate Zimbra 8.8.15 to Stalwart across 18 domains, with feature-parity tests and a domain-by-domain rollout; in progress.
Network Administrator, Five Cyber Host Security
Managed routers, VPNs, and firewall infrastructure across data centers. Hardened network security with custom firewall rules and intrusion analysis.
Projects and client work
Detailed project pages cover the architecture, responsibilities and current scope.
- Adastrion Core: deployed chat and coding agents with shared projects and isolated workspaces.
- Ledger: shared agent memory, research, handoffs and a daily AI-news pipeline.
- AutoLLama: local and distributed inference; four RTX 4090s behind LiteLLM, with 171 tok/s measured on Qwen3.6-35B-A3B using MTP speculative decoding.
- RADI: An internal research assistant for RADIOCOM procedures and regulations.
- Tire-sidewall recognition: From embossed sidewall text to structured, reviewable tire data.
- Leclinic network: Clinic network administration and a WireGuard connection to a software vendor.
- Radburg mail migration: An incremental migration from Zimbra 8.8.15 to Stalwart across 18 domains.
- PhotonSpark infrastructure: Compute, shared storage and network operations across a 15+ server fleet.
- Operations automation control plane: A Go orchestrator that separates proposed actions from execution policy.
- Electrical Age port: Bringing a Java/Kotlin circuit-simulation Minecraft mod to newer game versions.
- Audio-reactive ESP32 lighting: Two ESP32 controllers drive 800 LEDs from a subwoofer signal.
- SparkMC: Technical setup for a Minecraft community server.
- SparkTranscript: Romanian speech research and a medical-dictation website.
Skills
- Networking
- WireGuard, GRE, VLANs, FortiGate, nftables, pfSense, Cisco IOS, UniFi
- Infrastructure
- Kubernetes (K3s), Proxmox VE, Ceph, Docker, Ansible, Envoy, cert-manager
- Observability
- Prometheus, node_exporter
- Languages
- Go, Python, TypeScript/JavaScript, C, Java/Kotlin, Swift, Bash, SQL
- Data
- PostgreSQL (CloudNativePG), MySQL/MariaDB, Redis, FoundationDB, ArangoDB, Neo4j
- Vector databases
- Qdrant, pgvector
- AI and inference
- llama.cpp, vLLM, SGLang, LiteLLM, NVIDIA NeMo, RAG, hybrid retrieval and reranking
- AI agents
- Claude Code, Codex CLI, Hermes Agent, MCP servers, multi-agent pipelines
- Operating systems
- Linux, Windows Server, OpenBSD, Android, iOS
Teaching
CCNA Instructor, Hackademy, Faculty of Automatic Control and Computers, UNSTPB
- Delivered lectures on networking and hands-on labs with Cisco Packet Tracer.
- Built and maintain hackademy.ro with live seat counter and automatic capacity lock.
- Built an internal admin dashboard for events and registration management.
- Developed awg.sprk.ro for LAN events with real-time slot availability and auto-close at capacity.
- Organized LAN parties - managed matches, hosted servers, tracked points for prizes.
Education
Bachelor Degree in Computer Science, National University of Science and Technology POLITEHNICA Bucharest
Certifications and recognition
- Cisco Certified Network Associate (CCNA)
- Claude Code in Action
- Claude 101
- 1st, Cursor Hackathon Bucharest 2025
- 1st, Innovation Labs CyberHack 2024
- 2nd, HARD & SOFT 2025
- 2nd, EESTEC Olympics 2024
- Google VRP: reported a permissions bypass, June 2025