From business need to operating SaaS.
I designed and built zgloszenia24.pl from the ground up for Polish organizations that needed sign-ups, appointments, reservations, messages and payments in one operational system.
Founder ownership meant handling the whole lifecycle: product decisions, architecture, code, Linux servers, Docker, SSL, backups, monitoring, onboarding and support.
Payments with real invariants.
The ecommerce layer supports TPay OpenAPI, Stripe, BLIK, installments, invoices, payment requests, refunds and audit trails. Confirmed transactions are protected by domain rules rather than treated as ordinary editable records.
- Provider abstraction keeps business workflows independent from a single payment gateway.
- CSRF and session checks, rate limits and explicit authorization boundaries protect customer operations.
- Messaging through SMSAPI and Mailgun connects payment and reservation states to customer communication.
Built to keep changing.
The product has outlived multiple framework, infrastructure and payment-provider generations. Long-term maintenance has required disciplined migrations and modernization without destabilizing workflows customers already depend on.
The core domain was built years before modern AI tooling. Today I apply AI-assisted engineering and carefully bounded AI workflows to understand, test and modernize the legacy surface while preserving proven payment and booking rules.