SENIOR SOFTWARE ENGINEER

Svitla Systems Inc. is looking for a Senior Software Engineer for a full-time position (40 hours per week) in Argentina. Our client offers a comprehensive suite of billing, payments, and software solutions for professional services firms.

Requirements

Front-end experience

• Strong production experience with React, including modern hooks, suspense, and patterns.
• Solid grounding in performance, accessibility (WCAG), responsive design, and component architecture.
• Experience with enterprise component libraries (MUI, Radix UI, Shadcn) and data-heavy UI is a plus.

Back-end experience

• Strong production experience in .NET / C# (.NET 8 or later), building RESTful APIs and microservices following API-first principles.
• Strong knowledge of SQL Server, T-SQL, schema design, query performance tuning, and Entity Framework / ADO.NET.
• Experience with cloud platforms. AWS preferred (Lambda, ECS, RDS, SQS, S3, CloudWatch). Azure equivalents are fine.
• Architectural judgment on service boundaries, async messaging, caching, and consistency trade-offs.

Full-stack bar

• 5+ years of professional software engineering experience, with at least 2+ years of meaningful full-stack work. You’ve shipped features end-to-end, not just thrown code over the wall in either direction.
• Comfort being primary owner of a feature across both stacks. You don’t need a separate engineer to write the API for your UI or vice versa.
• Payments experience (strongly preferred)
• Hands-on Stripe integration in production. Embedded Checkout and Payment Element on the front. PaymentIntents, payment method cloning, refunds, and webhook handling on the back.
• Stripe Connect experience is a strong differentiator. Connected account creation, embedded onboarding components, direct charges, KYC and persons, capability and requirements webhooks, and payout bank attachment. Marketplace flows and multi-merchant architectures are a plus.
• Deep understanding of idempotency, retry safety, webhook signature verification, replay protection, and the failure modes of distributed payment systems.
• Experience integrating multiple processors behind one gateway, or running processor migrations, is a strong plus. So is embedded payment page architecture (iframes, postMessage).
• Familiarity with PCI-aware patterns. Tokenization, hosted fields, never touching raw card data, and the SAQ implications of how you build.
• Comfort with the operational side of payments. Partial captures, declined-card UX, disputes and chargebacks, and everything else that happens after the happy path.
• Exposure to ledgering systems or trust accounting is a strong plus.
• Cross-functional and quality
• Experience with CI/CD pipelines (AWS CodePipeline, TeamCity, GitHub Actions, or similar).
• Strong communication. You can explain a technical trade-off to a product manager and a junior engineer with equal clarity.
• Track record of mentoring peers and owning delivery outcomes inside an Agile team.
• AI-augmented development
• You actively use Claude Code, OpenAI Codex, Cursor, or similar AI coding assistants in your daily workflow. You can show how they’ve made you faster and more effective on both stacks.

Responsibilities

Build and ship money-movement features end-to-end

• Architect and build full-stack payment features (UI, API, service logic, data model) across the payments domain above, from invoicing and payment method management through payouts and reconciliation.
• Implement Stripe Elements, Payment Element, Checkout, and 3DS / SCA on the front-end while owning the matching PaymentIntents, webhook handlers, and persistence on the back-end.
• Build idempotent, retry-safe, observable payment workflows on the back-end and surface their state correctly on the front-end. Webhook-driven UI, optimistic updates done responsibly.
• Get ledger correctness right. Trust accounting means gross settlement, strict trust vs operating fund segregation, correct refund and chargeback routing, and statement descriptors that hold up to audit. Every cent lands in the right bucket, every time.
• Build merchant onboarding and KYC flows using embedded Stripe Connect components, with webhook-driven account status transitions handled correctly.
• Ship behind feature flags and entitlement gating. New payment capabilities roll out by region, brand, and package tier, and your code has to respect all three.
• Own data model design and migrations in SQL Server (T-SQL, Entity Framework) for the finance schemas you build.
• Drive front-end performance for payment surfaces. Core Web Vitals, bundle size, time-to-interactive. Conversion depends on it.
• Modernize both stacks
• Help migr