JExcellence
JExcellence
Full-stack · Oldenburg
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FULL-STACK SOFTWARE ENGINEER · OLDENBURG

Shops, payments, and SaaS that run reliably.

I build shops, payment integrations, and SaaS platforms with Java/Spring and React/Next.js, including tests, deployment, and ongoing care. Half-finished or AI-built projects I take into production.
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See my work
Taking enquiries · reply within one working day
2017first client project
20+completed projects
30+plugins in production
3payment providers integrated
§ ABOUT

Full-stack developer from Oldenburg, doing client work since 2017.

From the first email to running in production, you deal with the same person.
Justin Eiletz
since 2017client work
20+completed projects
DACHremote, on site in Oldenburg
DE · ENGerman native, English fluent
I'm Justin Eiletz. I started in 2017 with Minecraft plugins for server operators. Today I build shops, payment integrations, and SaaS platforms with Java/Spring and React/Next.js, from the data model to deployment.In my day job I'm a quality engineer at ab-data AG in Oldenburg, responsible for the abd-quality test toolkit. That shapes my projects: tests are written with the code, not after it, and I don't hand over anything I haven't checked myself.I hold two state-certified IT qualifications, I'm an ISTQB Certified Tester, and I co-founded AlphaOmega-IT GbR in 2022. Originally I'm from North Rhine-Westphalia.

I don't hand over code I wouldn't want to maintain myself.

MILESTONES
  1. 2017
    First client work: Minecraft plugins, more than 30 now in production
  2. 2022
    Co-founder and tech lead of AlphaOmega-IT GbR, until 2024
  3. 2023
    Quality engineer at ab-data AG, building abd-quality
  4. 2026
    Mythblock and Aveiro: own platforms with shop, payments, and AI features
§ WHO IT'S FOR

Four industries I work for regularly.

Each has its own page with process, examples, and a fixed price. Your case doesn't fit any of them? For any existing project, the tech check is the way in.
ANY INDUSTRY

Existing or AI-built project

Your shop or web app is almost done but doesn't run reliably. I review the code, hosting, and payment flow, tell you honestly where it breaks, and get the project production-ready.
Tech check · fixed price €890
Go to the tech check
STUDIOS AND BRANDS

Cosmetics & Beauty

You run a studio or your own brand and need an online presence with integrated booking — mobile, individual, no templates.
Entry-level offerBeauty Starter · Landing page with booking integration · fixed price €1,890
2 weeksTime to go-live
since 2023La Femme Kosmetik live
View details
MVP IN 8–10 WEEKS

Tech Startups

You're a founder who needs a working MVP — fast, cleanly built, demo- and investor-ready.
Entry-level offerFounder Sprint · Full-stack MVP · fixed price from €14,900
8–10 weeksTime to live demo
100 %Code and data ownership
View details
AUDIT AND MODERNISATION

Mid-sized Business

You operate mature software that's gradually becoming a bottleneck — replatforming, modernisation, or module extensions are on the agenda.
Entry-level offerCode audit + roadmap from €3,900 · smaller systems start with the €890 tech check
3–5 daysFrom access to audit report
ISTQBCertified Quality Engineer
View details
PLUGIN SUITES AND OPERATIONS

Gaming Communities

You operate a Minecraft server or gaming community and need reliable plugins that stay stable under peak load.
Entry-level offerPlugin Suite Bundle from €5,490 · individual plugins from €95 per hour
30+Plugins in production since 2017
10k+Players, across all servers
View details
§ EXPERTISE

Depth over breadth — with enough breadth to deliver.

Six focus areas from client work since 2017, each with one piece of evidence you can check.

  • Java Ecosystem

    9 years
    Spring Boot, Hibernate, JPA. Enterprise back-ends with clean layering and solid test coverage.
    EVIDENCERaindropCentral: Java 21, Spring Boot 4, Hibernate 6, and Flyway, built and run single-handedly. The JEHibernate library has 48 stars on GitHub.
    Spring Boot
    Hibernate
    JPA
    Maven/Gradle

  • Frontend Frameworks

    5 years
    React, Vue, Angular. Type-safe with TypeScript, modular components, sane state management.
    EVIDENCEAveiro (Next.js 16, React 19) and lafemmekosmetik.de are live. Plus pull requests to the open-source framework Once UI.
    React
    Vue
    Angular
    TypeScript

  • Quality Assurance

    3 years
    Test automation from unit to E2E. Selenium, Ranorex, Playwright, aqua cloud — ISTQB certified.
    EVIDENCEBuilt the abd-quality test toolkit at ab-data: regression cycles cut from several days to a few hours. ISTQB Certified Tester.
    Selenium
    Playwright
    Ranorex
    JUnit
    aqua cloud
    ISTQB

  • DevOps & Tooling

    4 years
    Containers, CI/CD, reproducible builds. Pragmatic pipelines without unnecessary complexity.
    EVIDENCERaindropCentral runs containerised with Docker under my own responsibility, from build to operations.
    Docker
    Git
    GitHub Actions
    Linux

  • Databases

    9 years
    MySQL, MariaDB, PostgreSQL, Oracle, MongoDB. Schemas that scale with growth without becoming a bottleneck in operations.
    EVIDENCEFlyway-versioned PostgreSQL schemas in RaindropCentral, Hibernate persistence in more than 30 production plugins with tens of thousands of users.
    MySQL
    MariaDB
    PostgreSQL
    Oracle
    MongoDB
    Redis

  • Engineering Craft

    9 years
    Code reviews, pair programming, mentoring. Software development is teamwork — including in solo engagements.
    EVIDENCECo-founder and tech lead of AlphaOmega-IT GbR from 2022 to 2024: Spring back ends, React and Vue front ends for client projects.
    Code Reviews
    Mentoring
    Architecture
    Refactoring
§ SELECTED WORK

What I've built.

Four projects you can look at live, plus six more from agency work, employment, and open source. Client work under NDA I'm happy to show in a call.
  1. Homepage of Mythblock
    OWN PRODUCT · 2026 – PRESENT

    Mythblock

    Shop · Payments · GamingOnline shop and platform for a Minecraft server. Spring Boot (Java 21) on the back end, Next.js 16 with Once UI on the front end. Payments via Stripe, PayPal, and Mollie (paysafecard) behind one gateway router, webhooks with signature verification and duplicate-event protection, a combined checkout for one-off purchases and subscriptions, and a voucher system. The game plugin talks to the shop through an HMAC-secured API. Runs on Docker Compose at Hetzner with nginx and nightly backups.Role: Architect · Solo developer · Operations
    Java 21
    Spring Boot
    Next.js 16
    Once UI
    PostgreSQL
    Stripe
    PayPal
    Mollie
    Docker
    Visit site
  2. Homepage of Aveiro
    OWN PRODUCT · PRIVATE BETA

    Aveiro

    SaaS · AI publishing platformAn AI-assisted publishing platform: site builder, CMS, blog, and newsletters in one workspace. Designed, built, and operated solo. Next.js 16 and React 19 on the front end, Supabase (PostgreSQL, Auth, Storage) on the back end, Stripe for billing, and the Vercel AI Gateway for text and image generation. Multilingual, built on Once UI. Currently in closed beta with invite and waitlist.Role: Architect · Solo developer · Operations
    Next.js 16
    React 19
    TypeScript
    Supabase
    Stripe
    Once UI
    Vercel AI Gateway
    PostgreSQL
    Visit site
  3. Homepage of RaindropCentral
    OWN PRODUCT · 2023 – PRESENT

    RaindropCentral

    Full-Stack · Enterprise · E-commerceAn enterprise platform — independently designed, developed, and operated. Java 21, Spring Boot 4, and Hibernate 6 in the backend with a Flyway-versioned PostgreSQL database, complemented by a Next.js 16 / React 19 frontend with Stripe checkout, live updates over WebSocket, an integrated shop, and Discord integration. Built as a personal reference project — now publicly available.Role: Architect · Solo developer · Operations
    Java 21
    Spring Boot 4
    Hibernate 6
    Next.js 16
    React 19
    PostgreSQL
    Stripe
    Docker
    WebSocket
    Visit site
  4. Homepage of La Femme Kosmetik & Beauty Suite
    CLIENT PROJECT · 2023 – PRESENT

    La Femme Kosmetik & Beauty Suite

    Landing Pages · BeautyLanding pages for cosmetics brands, each one built individually, never templated. La Femme Kosmetik opens the series: modern UI, integrated booking flow, consistently mobile-first. More beauty brands are shipped from the same studio.Role: Designer · Front-end developer
    Next.js
    TypeScript
    SCSS
    SEO
    Booking flow
    Visit site

More work

  • 2022 – 2024
    CO-FOUNDERAlphaOmega-IT GbR
    Co-founded and technically led an agency focused on custom web projects and professional Minecraft server operations. Spring back ends, React and Vue front ends, plus hosting and operations for community servers with tens of thousands of monthly active players.
    Co-founder · Tech lead
    React
    Vue.js
    Spring
    Hibernate
  • 2023 – PRESENT
    EMPLOYEDabd-quality @ ab-data
    Building and operating ab-data's in-house test automation toolkit, abd-quality. End-to-end suites with Selenium, Ranorex, Playwright, and aqua cloud. Regression cycles reduced from days to hours; flaky tests systematically stabilised.
    Quality engineer · ISTQB
    Selenium
    Playwright
    Ranorex
    aqua cloud
  • 2025 – PRESENT
    OPEN SOURCEOnce UI · Open-source contributions
    Active contribution to the Once UI framework — the design system this site itself is built on. Component pull requests, bug fixes, and contributions to discussions on API design and theming architecture.
    Contributoronce-ui.com
    React
    TypeScript
    SCSS
    Open source
  • 2017 – PRESENT
    CLIENT WORKMinecraft Plugin Suite
    More than 30 production plugins, built for server operators since 2017, serving tens of thousands of users. Hibernate-backed persistence, custom game mechanics, performance tuning for peak loads. This is where my Java, Hibernate, and architecture skills grew under real load — and the environment continues to serve as a testbed for new ideas.
    Plugin architect
    Java
    Paper / Bukkit
    Hibernate
    MySQL
  • BUILT SEVERAL TIMES
    CLIENT PROJECTSSoftware Licensing Server
    Licensing servers with key rotation, hardware binding, an admin dashboard, and API integration. Delivered multiple times for different clients — each iteration building cleanly on the lessons of the previous one.
    Designer · Backend developer
    Spring
    PostgreSQL
    REST
    Vue
  • 2024 – PRESENT
    OWN TOOLEnhanced Website Builder
    A drag-and-drop website builder with a component library, live preview, built-in SEO controls, and theme management. Originally conceived as an internal tool — in practice, it underpins projects where clients explicitly want to avoid templates.
    Architect · Full development
    React
    TypeScript
    Node.js
    PostgreSQL
Request full portfolio
§ HOW IT WORKS

How a project with me runs.

Four steps, each with a result that belongs to you. After every step you decide whether to continue.
  1. 01
    1–3 working days

    Analysis

    For existing code I review the repository, hosting and connected services. For a new project we settle what the first version must do and what it deliberately won't.
    You getReport with risks and a prioritised action list
    I need from youRead access to code and hosting, a one-hour call
  2. 02
    2–3 working days

    Quote

    Based on the analysis you get a written quote with scope, fixed price, timeline and acceptance criteria. Anything that can't be scoped cleanly up front is listed as a time-and-materials item with a budget cap.
    You getFixed price, milestones, clear acceptance criteria
    I need from youFeedback on scope, sign-off
  3. 03
    in stages

    Build

    I work on a staging environment you can open at any time. Each stage ends with a short demo and a status report. The code lives in your repository from day one.
    You getTested code, staging access, status reports
    I need from youFeedback on each stage, content such as copy and images
  4. 04
    ongoing afterwards

    Go-live and care

    Go-live with a rollback plan, documentation and a handover of all access. 30 days of bug fixing are included, after that an optional care plan at a fixed monthly price.
    You getLive system, documentation, all access
    I need from youSign-off
§ PRICING

What it costs.

Three hourly rates as the basis, with fixed prices built on top. “From” prices cover a tightly defined scope and become binding after the analysis.

Hourly rates

For work that can’t be scoped cleanly up front: finishing touches, change requests, debugging. Billed in 15-minute increments with a time log.
Development
€120per hour
Frontend, backend, bug fixing, and code reviews in Java/Spring, React, Vue, Angular, or Next.js.
Day rate (8 hours)€920
Complex development and consulting
€140per hour
Payment and shop logic, integrations, migrations, performance and security, decisions with long-term impact.
Day rate (8 hours)€1,080
Architecture
€150per hour
System design, data model, technology choices, and documented architecture decisions.
Day rate (8 hours)€1,150
RECOMMENDED STARTING POINT

Tech check

Up to one working day with your code, hosting, and connected services. Afterwards you know where you stand and have a fixed-price quote for the next steps.
Request a tech check
Fixed price€890
  • Traffic-light rating per area: code, security, payments, operations
  • Prioritised action list with effort estimates
  • A 5–8 page report that belongs to you
  • Fixed-price quote for the implementation

Analysis and consulting

  • Code audit and roadmapIn-depth codebase analysis with refactoring backlog, effort estimate, and cost range.3–5 WORKING DAYS
    from€3,900
  • Architecture reviewOne working day with your system architecture, followed by written recommendations.1 WORKING DAY
    Fixed price€1,490
  • Tech strategy workshopTechnology choices, roadmap, and priorities, with preparation and minutes.1 DAY
    Fixed price€1,690
  • Pair programmingFour hours on a shared screen in your codebase.4 HOURS
    Fixed price€560

Implementation

  • Stripe integration, basicCheckout, webhooks without double charges, order confirmation email, go-live.1–2 WEEKS
    from€1,900
  • Stripe integration, extendedPlus variants, coupons, Stripe Tax, invoices, refunds, or subscriptions.2–4 WEEKS
    from€4,500
  • Shop completionMake half-finished or AI-built shops production-ready: bugs, tests, payment flow, deployment.AFTER TECH CHECK
    On request
  • Landing pageYour own site with services, about, and contact, mobile-first.2–3 WEEKS
    from€2,900
  • Multi-page website5–8 pages with a headless CMS, bilingual on request.4–6 WEEKS
    from€6,900
  • Full-stack web appBackend, frontend, database, login, and payments, for example a SaaS product.AFTER DISCOVERY
    On request

Care after go-live

Fixed response times on working days. Three-month minimum term, then cancellable monthly. Additional hours cost €110
Basic
So nothing breaks unnoticed.
€290per month
  • Uptime and error monitoring
  • Monthly security and dependency updates
  • Backup checks
  • 1 hour for small fixes
  • Response within 2 working days
Ask about care
Standard
Recommended
For shops and sites where something changes regularly.
€890per month
  • Everything in Basic
  • 8 hours for bugs, small features, and changes
  • Unused hours roll over for one month
  • Response within 1 working day
  • Short monthly report
Ask about care
Plus
For applications under continuous development.
€1,690per month
  • Everything in Standard
  • 16 hours per month
  • Planning of the next development stages
  • Response within 1 working day
  • Monthly call
Ask about care
Without a care plan: bug-fix timebox of up to 4 hours for €480 at a fixed price, starting within 2–3 working days.
Not sure what fits? Describe briefly what it’s about and you’ll get an assessment within one working day.
Discuss your project
All prices are final. No VAT is charged under § 19 UStG (German small-business rule).
§ CONTACT

Tell me what you're working on.

You write to me directly, not to an agency. Three or four sentences are enough to start.
Justin EiletzFull-stack software engineer · Oldenburg
What happens next
  1. 1
    You describe the project brieflyWhat should be built or fixed, what already exists, and by when. A link to the site or repository helps.
  2. 2
    I reply within one working dayWith follow-up questions or a proposed time for a free 30-minute call.
  3. 3
    You get a concrete offerFor existing code usually the €890 tech check first, otherwise a direct quote with scope and fixed price.
Email
justin.eiletz@jexcellence.de
Write an enquiry by email
Reply within one working day. The first call is free and non-binding.
Other ways
Phone · +49 1577 0433689Call back by appointment, arranged by email
GitHub · jexcellenceCode and open-source libraries
Instagram · @jexcellence_A look at current projects