Fintech · Investments · Aug 2025 – Present
Sole backend engineer
An investment platform where individuals and companies fund multi-currency wallets, invest in fixed or flexible plans, earn scheduled interest, buy utilities and withdraw to bank accounts or crypto wallets, run with a licensed securities brokerage.
01 / scope
02 / architecture
Clients
API
Async work
Data
Third-party services
03 / engineering notes
A once-a-day job paid everyone at 1 AM, so someone who invested at 2 PM was paid 11 hours early. I moved interest to an hourly scheduler that checks how long each investment has actually been running, so every investor is paid on their own cycle.
Every payment-provider webhook is stored as a receipt and processed once, even if it arrives twice. Utility purchases debit the wallet atomically before the provider is called and refund automatically on final failure, and requery jobs resolve transactions stuck in a pending state.
KYC callbacks, deposits, payouts, interest runs, referral settlements and emails all happen in background workers with retries and exponential backoff. Each worker runs as its own Docker Compose service, so a slow provider never blocks a request.
04 / stack