Full Stack Engineer - Platform (Intermediate-to-Senior)
littlefish
Marketing & Communications, Software Engineering
Sterling, VA, USA · Remote
Posted on May 11, 2026
About littlefish
littlefish is a Unified Commerce Platform for small and medium businesses across Africa, distributed through Financial Institution partners — banks, telcos, and insurers. We are live with 3 of the 5 major South African banks and onboarding 10–12 FI clients across the continent. The platform gives SMEs access to payments, invoicing, stock management, and expense management — tools previously only available to large corporations.
We are an AI-native engineering team. Every engineer operates as an Intent Architect: directing AI with precision, owning every decision about correctness, security, and quality, and building software that impacts real businesses across Africa. We are not vibe coders. The AI accelerates execution. The engineering judgment is yours.
Role Summary
The Full Stack Engineer is a core contributor to the design and delivery of the littlefish platform. This is a hands-on, high-ownership role spanning .NET / C# microservices, React portals, and Flutter merchant and POS apps.
This is the rare profile that operates with depth across the entire platform — not a generalist who knows a little of everything, but an engineer with genuine architectural instinct in the backend and the breadth to direct AI confidently across web and mobile when work crosses layers. At littlefish, most features do.
You think architecturally before you build, direct AI with precision, and review every line of generated output against your intent, the existing system, and the security requirements of a regulated fintech. The quality of what ships under your name is a direct reflection of the quality of the thinking behind it.
Key Responsibilities
Solution Design & Architecture
Decompose problems and articulate the correct implementation approach before a single prompt is written.
Produce clear design artefacts — architecture diagrams, API contracts, data models, event schemas — that encode the constraints AI will be directed against.
Evaluate trade-offs across service boundaries, data models, integration patterns, and build vs. buy in a multi-tenant fintech context.
Champion engineering standards: security patterns, observability, idempotency, transactional integrity, pattern consistency.
Collaborate with the Principal Architect on decisions that cross service boundaries or set new platform patterns.
Senior engineers are expected to drive end-to-end solution design for major features and lead cross-functional design reviews.
Backend Development
Design, build, and maintain scalable C# / .NET 9 microservices that power the core platform.
Own the full request lifecycle: API design, business logic, data persistence, observability, error handling.
Build event-driven flows on Pub/Sub with appropriate consistency guarantees, retry semantics, and dead-letter handling.
Implement integrations with payment gateways, core banking systems, and FI partner APIs — REST, webhooks, message-driven — built for idempotency, resilience, and observability.
Direct AI to generate tests; validate they cover the failure modes that matter, not just the happy path.
Frontend & Mobile Development
Build and maintain web frontends (merchant portal, FI admin portal) using React and TypeScript, following component-driven design.
Develop cross-platform mobile features in Flutter / Dart for the POS terminal app and merchant companion app.
Translate Product and Design intent into polished interfaces — and evaluate whether AI-generated UI is correct for the user, the FI context, and the business case.
Maintain visual consistency across white-labelled deployments per FI client.
Handle the realities of fintech UX: auth flows (Keycloak, Firebase, Azure Entra), async data, error states, constrained POS hardware.
AI-Native Engineering Practice
Direct AI with precise, contextual prompts that encode system knowledge and the constraints of the regulated environment.
Review all AI-generated output critically — correctness, pattern alignment, security implications, edge cases.
Contribute to and uphold the team's evolving AI tooling standards, prompt review practices, and output quality gates.
Integrations
Design and implement integrations across the broader ecosystem: payment processors, FI core systems, voucher providers, ERPs, and other third-party platforms.
Build resilient integration patterns and ensure data contracts are well-defined, versioned, and backwards-compatible.
Contribute to API-first design using OpenAPI / Swagger standards.
Trace cross-system failures and distinguish integration contract issues from upstream data problems.
Infrastructure & Platform Awareness
Work confidently within the GKE / GCP infrastructure that hosts the platform, with Azure DevOps CI/CD pipelines.
Engage with platform tooling: managed databases (MongoDB Atlas, PostgreSQL, Redis), Cloud Storage, Secret Manager, Cloudflare edge.
Write services with observability in mind — structured logging, distributed tracing (OpenTelemetry → Dash0), meaningful alerting.
Collaborate with SRE and DevOps on deployment configurations, failure modes, and incident response.
Collaboration & Delivery
Work in cross-functional squads alongside Product, Design, QA, and SRE/DevOps.
Participate in agile ceremonies: sprint planning, stand-ups, retrospectives, technical reviews.
Mentor intermediate and junior engineers — particularly on the discipline of directing AI well rather than just writing code.
Contribute to internal documentation, runbooks, and incident post-mortems.
Ask about the FI requirement, the SME use case, and the product goal before you build.
Skills and Qualifications
Experience
4–10 years of professional software development experience, with clear progression from intermediate to senior level.
Strong, demonstrable proficiency in C# and .NET — your primary backend language and where your depth runs deepest.
Hands-on experience building and consuming REST APIs and third-party integrations (payment APIs, banking APIs, or similar).
Production experience with React and TypeScript.
Working competence with Flutter and Dart for cross-platform mobile.
Experience with relational and document databases (PostgreSQL, MongoDB), query optimisation, and ORM usage.
Hands-on experience with GCP (or equivalent) and containerisation with Docker / Kubernetes (GKE).
Proven ability to lead solution design discussions and document architectural decisions clearly.
Fintech, payments, or banking experience strongly preferred.
Technical Skills
Backend: C# / .NET 9, ASP.NET Core, Entity Framework Core, async patterns, microservices.
APIs & Integration: RESTful design, OAuth 2.0 / JWT, OpenAPI / Swagger, idempotency, eventual consistency.
Frontend: React, TypeScript, component-driven architecture, state management.
Mobile: Flutter, Dart, mobile state management, secure storage for financial flows.
Cloud & Infrastructure: GKE / GCP, Docker, Azure DevOps CI/CD, GCP Secret Manager, Cloudflare.
Data: MongoDB, PostgreSQL, Redis — query design and performance for multi-tenant workloads.
Messaging: GCP Pub/Sub, event-driven patterns.
Observability: OpenTelemetry, Dash0, structured logging, distributed tracing.
Auth: Keycloak, Firebase, Azure Entra ID.
AI tooling: practical fluency with AI-assisted development workflows — prompt design, output review, and the discipline of directing AI rather than being directed by it.
Soft Skills & Leadership
Architectural thinking — decompose, identify boundaries, define constraints, and articulate the correct approach before building.
Genuine review rigour — substantive checks against intent, existing patterns, and security implications.
Ownership — quality, security, test coverage, and pattern consistency across everything you ship are your problem to solve.
Curiosity about the business — you ask about the FI context and the SME use case before you build.
You feel the weight of what the software does — when the platform is down, SMEs cannot trade.
Clarity — you simplify complexity for engineers and non-technical stakeholders alike.
Constructive challenge — you raise risks, say no with reasoning, defend decisions on substance.
Senior bias for finishing and mentoring — you leave things better than you found them and contribute to a culture of engineering excellence.
To apply, please send your CV and a short note on why littlefish to hiring@littlefishapp.com. We do not require cover letters, but we do want to know what draws you to this role specifically — curiosity about the problem is part of what we are hiring for.
