What We Do Best

Three areas where we have deep expertise and a production-proven track record.

FinTech & Payment Systems

We built a 41K-line accounting suite with ELSTER XML generation for 3 German tax forms, XRechnung 3.0 e-invoicing, DATEV export, and SKR04 chart of accounts — supporting 5 countries via plugin-based architecture. Plus a stablecoin payment platform with AES-256-GCM encrypted wallets and an append-only double-entry ledger.

app.grundlabs.de

#847Acme Corp€12,400Paid

#846TechStart€8,200Pending

#845FinGroup€25,000Paid

ELSTER Tax Filing (UStVA, USt, EÜR)
SEPA Payments (PAIN.001/008)
Stablecoin Payment Processing
Multi-Country Accounting (5 countries)

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📊Business Analytics 🧾Invoice & Billing

Booking & Marketplace Platforms

Our hotel platform: 82K lines, 329 API routes, concurrent booking prevention, 4-tier loyalty program, QR check-in, and OTA channel sync. Our gig marketplace: 31K lines, Stripe escrow with 289 API endpoints, real-time messaging, and 4-language i18n. Both handle concurrent transactions at scale.

10:00Dr. SchmidtConsult

11:30Team SyncMeeting

14:00Maria K.Review

Concurrent Booking Prevention
Stripe Escrow & Payouts
OTA Channel Manager Integration
4-Tier Loyalty & Dynamic Pricing

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📅Appointment Scheduler 👥Resource Planner

Mobile App Development

Native-quality iOS and Android apps from a single codebase. We've shipped ride-sharing apps with real-time GPS tracking and map integration, staff booking apps with availability calendars and push notifications, and payment apps with biometric auth and QR scanning. All connected to our production backends.

Push notificationsFCM

Biometric authnative

Offline-first synclocal

iOS & Android from One Codebase
Real-Time GPS & Map Integration
Push Notifications & Biometric Auth
Offline-First with Background Sync

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🚗Ride Tracker 💳Mobile Wallet

Custom Platform Development

Beyond our core verticals: a ride-sharing platform with PostGIS spatial queries and 5-model pricing engine (26K lines). A team chat with Discord-compatible webhooks and 21 WebSocket message types. An AI agent daemon with 18 built-in tools and 3 LLM backends. A cloud migration SaaS with BSI/GDPR compliance checks.

Auth module deployed2m

PR #42 merged1h

Sprint review done3h

PostGIS Spatial Queries & Routing
WebSocket Real-Time Systems
AI/LLM Tool Integration
BSI/GDPR Compliance Automation

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📋Project Management ⏱️Time Tracker 🤝CRM & Sales Pipeline 🎫Support Ticketing

SaaS Platforms & Developer Tools

Our infrastructure platform: 360K lines of code, 931 API endpoints, multi-tenant silo architecture with Stripe billing. Our cost optimization SaaS: 105K lines, configurable optimization rules, 6 billing tiers, RBAC, OIDC/SAML/LDAP auth, and a CLI tool. Both in production.

Multi-Tenant Silo Architecture
Stripe Billing (6 plans, usage metering)
CLI Tools & Rules Engine
RBAC, OIDC, SAML, LDAP Auth

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₿Crypto Portfolio

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