Petre Diaconescu
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Senior Java / Spring Boot Consultant & Architect

Enterprise Java & Spring Boot architecture for high-throughput, regulated systems.

10+ years delivering scalable backend services in banking, telecom and rail. I specialize in Java 21 upgrades, OpenShift cloud-native migrations, event-driven architecture on Kafka, and integrating AI into core workflows.

Discuss a project See case studies

Remote, EU-basedB2B freelance & consultingEnglish · Romanian

Illustration · event-driven order flow, Spring Boot services on Kafka
  • Java 21
  • Spring Boot
  • Kafka
  • OpenShift
  • Spring AI
10+ years
enterprise backend systems
Java 8 → 21
live enterprise migrations
CH · IE · RO
Switzerland, Ireland, Romania
Regulated
banking, telecom, rail

Services

Backend engineering for systems that cannot go down

Hands-on delivery inside your team or a focused engagement with a clear outcome. The common thread is reliable Java services in environments where security, audit and uptime matter.

modernization

Modernization & Java upgrades

Move live platforms from Java 8 to 21 without stopping delivery. Refactor legacy code, tune performance and put dependable CI/CD in place.

  • Java 8 → 21
  • performance tuning
  • CI/CD
  • legacy refactoring

cloud-native

Cloud-native & microservices

Migrate monoliths and legacy platforms to the cloud. Design event-driven flows with Kafka / MQTT and clean REST APIs between services.

  • cloud migration
  • Kafka event-driven
  • REST APIs
  • microservices

security

Enterprise security & compliance

Backend work for banking and compliance systems: Spring Security, role-based access, audit logging, and integrations for fraud detection.

  • banking systems
  • fraud detection
  • Spring Security
  • role-based access control

applied AI

Applied AI integrations

Connect AI services to Java backends with the same standards as the rest of the platform: secure APIs, access control, audit logging and monitoring.

  • Spring AI integrations
  • secure AI APIs
  • access control & audit

Case studies

Selected engagements

Client names are withheld under confidentiality agreements. The scope and the work are described as delivered.

rail2025 – now

Cloud migration for a European rail operator

Context
A data-intensive, event-driven backend for a major European railway provider, moving off a legacy platform.
Work
Stabilization and new development, throughput improvements, and support for the migration to OpenShift. Defect resolution through the transition phases.
Outcome
Higher throughput on the event pipeline and a steadier path from legacy to cloud-native.

Kafka · Spring Cloud Stream · OpenShift

telecom2022 – 2024

High-volume sales platform for a telecom

Context
A large European telecom's sales and customer management platform, running on Java 8.
Work
Led the upgrade from Java 8 to Java 21. Designed REST APIs for high-volume workflows, built CI/CD pipelines and handled production incidents.
Outcome
Better performance and long-term supportability on a modern Java runtime, with faster diagnosis of production issues.

Java 21 · TeamCity · Dynatrace · Kibana

banking2021 – 2022

Online banking for a Swiss financial institution

Context
A large online banking platform in a security-critical environment, delivered with onshore and offshore teams.
Work
Backend features secured with Spring Security. As primary on-site developer in Zurich, coordinated releases with offshore teams.
Outcome
Stable releases backed by testing, code review and production support.

Spring Security · release management

Experience

A decade inside large, regulated systems

  1. Jan 2025 – now

    Senior Java / Spring Boot Engineer

    Accenture · major European railway provider · Remote Kafka · Spring Cloud Stream · OpenShift
  2. Sep 2022 – Dec 2024

    Freelance Java / Spring Boot Consultant

    Large European telecom company · Remote Java 21 · TeamCity · Bitbucket · Dynatrace · Kibana
  3. Jan 2021 – Jun 2022

    Senior Java / Spring Boot Engineer

    Accenture AG · major Swiss financial institution · Zurich Spring Security · code review · production support
  4. May – Nov 2020

    Freelance Java / Spring Boot Consultant

    Large European investment bank · Remote

    Anti-money-laundering and fraud detection systems. REST integrations between compliance services and core banking.

    Kafka · REST integrations · security checks
  5. Dec 2017 – Oct 2019

    Freelance Java / Spring Boot Consultant

    Financial services & startup clients · Ireland

    REST APIs and microservices across several client projects, including a major French banking group.

    Microservices · Spring Boot
  6. Jul 2016 – Nov 2017

    Full-stack Software Engineer

    Equifax · Dublin

    Enterprise applications in a large data environment, from Java services to Angular front ends. Proposed the frontend and backend decoupling that let teams ship independently.

    Java · Angular · TypeScript
  7. Aug 2015 – Jul 2016

    Software Developer

    Credit Europe Bank · Romania

    Designed and built an internal document archiving system from scratch, with role-based access control, audit logging and REST endpoints.

    Document management · RBAC · AngularJS

Skills

Tools I work with every day

Core & frameworks

  • Java 8–21
  • Spring Boot
  • Spring Security
  • Spring Cloud
  • REST APIs
  • Microservices

Data & messaging

  • Apache Kafka
  • PostgreSQL
  • Oracle
  • MongoDB
  • Redis
  • Neo4j

Platforms & tools

  • OpenShift
  • Docker
  • Jenkins
  • TeamCity
  • Dynatrace
  • Kibana
  • Grafana
  • JUnit
  • Mockito

Contact

Need to modernize an enterprise system or build a reliable backend architecture?

Send me an email or a message on LinkedIn with a short description of the system and what needs to change, and we'll set up a call.

Emailcontact@diaconescu.dev LinkedInlinkedin.com/in/petrediaconescu Message me on LinkedIn Open for EU-based B2B freelance contracts & consulting projects.