Dimitrios Dalaklidis

Due to the recent shortages in the Greek healthcare system, I was inspired to create an original software that manages hospital patients to be used by clerks and Doctors alike. To that end, I used Secure REST API for said managing of patients, but also hospitalizations as well as medical tests. The software features stateless JsonWebToken authentication, role based access control (DOCTOR / CLERK / ADMIN) enforced at the HTTP method level and atomic patient registration(for every individual person that is) via Spring @Transactional. Lastly, It includes a full Luhn algorithm implementation for validating Greek ΑΜΚΑ numbers with birth date extraction. Last upgrades include unit tests with JUnit 5 and Mockito.

API Gateway for routing requests to backend services with resilience and control features. Includes rate limiting (Redis sliding window with Lua), retries with exponential backoff, circuit breaker (CLOSED/OPEN/HALF-OPEN), JWT authentication, tested to ensure security and response caching. Provides admin endpoints for monitoring (metrics, circuit states, rate limits) and a mock service for failure injection and testing. Built with the aim of easing the growing issues regarding traffic in large systems(ie Netflix type services).

Multithreaded HTTP server written from scratch in C using Windows sockets (Winsock). Handles concurrent connections entirely without a framework: raw socket management.

Unix Process Management demonstrates Unix interprocess communication using a shared pipe across multiple child processes. Covers the full process lifecycle: creation, concurrent execution, and synchronization via fork(), getpid(), pipe(), and wait(). Packaged with a multi stage Docker build; no local C toolchain required. Using Docker we are able to reduce overall size by more than 70 percent and significantly reduce the attack surface. This repository was heavily inspired by the brilliant book of Andrew S. Tanenbaum and Herbert Bos, "Modern Operating Systems" .

My second ever app and a big learning experience, It has been modernized recently with Docker as have most of my projects in a conscious effort to get acquainted with newer technology. TCP client server application. The client sends integers over a socket and then the server computes and returns their prime factors. Built for the distributed systems course at UowM. This was the equivalent to beginner calculator apps, only difference being that this is at the low-level.

Process supervisor written in Bash for managing and autorestarting long running workloads in Docker and Kubernetes environments.

Full library management system with Swing GUI and MySQL backend. Features user authentication, book search, borrowed book tracking and automated database initialization via SQL schemas.With this one, I wanted to prove that although I am a young engineer I can still work with legacy technology like SWING.