Critical Infrastructure

The Problem

A bank had a QR-code access control system that crashed every few hours. Staff had to manually restart the server in the middle of the working day. Code analysis revealed two issues: a memory leak in a loop that never released database connections, and zero input validation on QR codes — anyone could submit an arbitrary string and crash the system.

At the same time I was working on a luxury apartment complex and a jewelry store: three completely different contexts, each with specific security requirements and infrastructure to build from scratch.

The Solution

For the bank I rewrote the QR management system: connection pooling with proper cleanup, strict input validation with a fixed schema and cryptographically signed expiration. Zero downtime since it went live.

For the jewelry store I installed a people counting system with Hikvision cameras and zone heat mapping. The system generates retrospective reports showing which areas receive the most traffic by time slot. This data allowed the owner to reposition high-value items in the highest-visibility zones.

For the residential complex I designed the entire network and security infrastructure: managed switches with separate VLANs for apartments, cameras, intercoms, and guests. Each apartment is isolated from the others at the network level. PTZ cameras on Ajax NVR, IP video intercoms with remote response from smartphones. Not just software configuration: I pulled the cables, installed the racks, configured every switch.

The Result

The bank has operated without interruption since the system was rewritten. The jewelry store repositioned its highest-value items into the highest-visibility zones based on the heat-mapping data. The residential complex has a fully segmented network with 24/7 monitoring and zero security incidents.