Subcontracting · software houses and IT consultancies

Senior hands for your client projects, invoiced company to company

I am Jyri, a full stack developer with nine years and more than a hundred delivered projects: ERP, CRM, banking and POS integrations, and AI in production. I join your team and build what the project needs, in your tools and on your client's terms.

Within a weekstart
€70/h excl. VATrate
IT2018 or yourscontract
Remote or hybridmode

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Areas

Pick the area closest to your task: each page has its own examples and a short CV for it.

PythonBack ends, integrations and data: Django, Flask, FastAPI.Laravel and ReactOperational software and web apps with complex workflows.AI engineeringLanguage models and computer vision into production, €80/h.IntegrationsERP, banks and POS without duplicates or lost rows.Online storesWooCommerce and ERP integrations for agencies, white label.

Projects that relate to this

Three long projects where I owned everything from the data model to production. All of them are in use today.

Editori: construction ERP

Architect & lead developer · In production · 2021–2026

The full lifecycle of facade renovation and apartment reconstruction in one system, originally the “Westface site editor”

A configurable state machine: status groups, status logic and status types, plus a change history for every entity (element, apartment, room, ticket, company). The customer defines their own workflows without a code change.
Permissions on two levels: spatie/laravel-permission on the back end and CASL on the front end, with per-project roles. The same user can be a foreman on one project and a viewer on another.

111Eloquent models248API routes3apps, 1 API

Laravel 10PHP 8.2MySQL 8Redis 7React 18TypeScriptRedux ToolkitKonva

Why it matters: Complex operational software in Laravel and React: the level client work expects.

B2B CRM & lead automation

Architect & sole developer · In production · 2026 to present

Lead acquisition, enrichment, campaign sequences and a sales pipeline on one platform

A campaign engine: multi-step sequences, message variants with A/B testing (multi-armed bandit), condition-based branches, automatic actions and recipient enrollments.
An enrichment chain where every contact passes through paid and free sources (PDL → Hunter → ZeroBounce → Gemini) until it has a verified, deliverable email address and a reasoned company context.

39+domain models

PythonFlask 3.1SQLAlchemy 2.0PostgreSQL 16React 19Vite 8CeleryRedis

Why it matters: Python, React and integrations with dozens of APIs, running every day.

Automated accounting system

Architect & developer · In daily use · 2026 to present

End-to-end bookkeeping automation for a sole trader, a limited company and a personal account.

Bank-statement retrieval and parsing: Nordea (CSV / JSON) and Holvi (XLSX / JSON). The limited company has two Holvi accounts (main and tax reserve), of which only the main one is published to the ledger while the reserve is tracked as a budget.
A VAT engine: rates and tax classes, reverse-charge VAT, pension-scheme expenses, a counterparty map and rules that live in configuration rather than in code.

2banks integrated0duplicates (idempotent)

PythonGmail APIGoogle Sheets APINordeaHolviFirefly IIISQLiteGemini

Why it matters: Bank connections and accounting rules: an area where mistakes cost money.

How we start

The goal is a useful commit in your repository during the first week.

Send the task and the stack

In a few lines: the project, the technologies, the timeline. I answer the same working day with my CV and the two closest examples of my work.

A scoped first week

I start with a small, clearly bounded task in your repository and your tools. At the end of the week you see the code and decide what happens next.

Invoices every two weeks

Hours go into your tracker, the invoice comes from GG Solutions Oy. No lock in: we continue for as long as it is useful to you.

Terms

Trial week: 25 hours on a bounded task, fixed €1,750 excl. VAT
Rate: €70/h excl. VAT; longer engagements or a fixed scope are agreed separately
Invoicing: GG Solutions Oy, Finnish Business ID 3465139-7, every two weeks by the hour; EU reverse charge where it applies
Contract: IT2018 terms or your own template; confidentiality, and the rights to the code are yours
Capacity: 20 or 40 hours a week, usually starting within a week
How: Remote, or hybrid from Helsinki; your repositories, tickets and chat
Languages: English, Finnish and Russian

Questions

Are you a freelancer or a company?

A company: GG Solutions Oy, Finnish Business ID 3465139-7. I invoice hours or an agreed scope. I am not looking for employment.

What do you not do?

Java, .NET, native mobile and PLC programming. The core is Python, PHP and Laravel, React and TypeScript, PostgreSQL and MySQL, Docker and AI integrations.

Can your end client interview you?

Yes. Many end clients want their own interview and a CV with references, and both are fine.

What if it does not work out?

The first week is a bounded task. If the result does not convince you, we stop there and you pay only for the hours worked.

Which time zone?

Central and Northern European working hours are covered. I work remotely, or hybrid from Helsinki.

Tell me about the project and I will tell you where I can help

Send the stack, the timeline and the task in a few lines. You get my CV and the two closest examples the same working day.

jyri.gromyko2002@gmail.com +358 44 978 2028

Tell me about the project Download CV (PDF)

Other pages

Full CV and all projects Python development as a subcontractor Laravel and React as a subcontractor AI engineering as a subcontractor Integrations: ERP, banks and POS WooCommerce development for agencies AI for everyday business work