Katerina Sh Start a project
Freelance Full-Stack Engineer · Available for projects

Full-stack engineering for business-critical web applications.

I design and build complete web applications — from user-facing interfaces and internal tools to APIs, databases, integrations, and background workflows. The result is software that works as a whole and remains maintainable after launch.

Let's build something reliable  → Explore capabilities
End-to-end
FRONTEND · BACKEND · DELIVERY
Backend depth
APIS · DATABASES · DISTRIBUTED SYSTEMS
AI-ready
RAG · LLM INTEGRATIONS · WORKFLOWS
Built to last
RELIABILITY · PERFORMANCE · MAINTAINABILITY
01 — Capability Map

How the pieces connect into working systems

Explore the systems I can build and the technologies behind them. Switch between solution and technology views, then select any capability to see how it contributes to a complete product.

View
CoreFull-Stack
Full-Stack Web Apps
SaaS & B2B Platforms
Complex Product Features
Admin Panels
Internal Tools
Background Workflows
Reporting & Exports
APIs & Integrations
Real-Time Features
Auth & Access Control
AI & Knowledge Systems
Refactor & Rescue
Performance & Scale
Database Optimization
Architecture Modernization
02 — What I Can Help With

Concrete problems, solved end to end

01

Build a full-stack web application

Turn a product idea or business workflow into a complete application with its interface, backend, data model, integrations, and deployment foundations.

02

Build or improve a backend

Design new services or strengthen an existing backend with reliable APIs, business logic, background processing, data access, and maintainable architecture.

03

Develop complex product features

Add workflows, editors, dashboards, real-time communication, reporting, data processing, and other features that need coordinated work across the stack.

04

APIs & integrations

Design reliable APIs and connect your product to external services, identity providers, storage, messaging, payments, maps, or business platforms.

05

Admin panels & internal tools

Replace spreadsheets and disconnected manual processes with interfaces designed around the way your team actually works.

06

Improve an existing system

Diagnose and repair architecture, performance, and maintainability problems without a full rewrite.

07

AI and knowledge systems

Build RAG assistants, document search, AI-enabled workflows, function-calling integrations, and LLM features tied to a real product or operational need.

08

Data processing and background workflows

Build import and export pipelines, scheduled jobs, queues, long-running processes, reporting flows, and systems that transform or synchronize large volumes of data.

03 — Selected Work

Proof, not promises

P—01API Platform

Multi-Tenant API Platform

Problem — multiple clients needed to use one API product without exposing data, access, or processing workflows across organizations.

Solution — built a shared API platform with client-specific environments, JWT-based authentication, role-aware access control, configurable input normalization, tenant-specific processing, and isolated service and database layers.

.NETPostgreSQLJWT AuthRole-Based AccessGCP
Which regions support same-day fulfillment?
Same-day is live in 4 metros, expanding to 7 next quarter.
ops-guide.pdf rollout-q3
P—02AI · Retrieval

Retrieval-based knowledge assistant

Problem — critical answers were buried across years of documents, wikis, and tickets.

Solution — a retrieval-augmented assistant that answers in context and cites its sources every time.

PythonpgvectorReact
ORDERS
1,284
SLA
99.4%
QUEUE
6
P—03Operations UI

Dashboards & Admin Systems

Problem — business teams needed one place to manage users, projects, statuses, assignments, reports, and operational data instead of relying on disconnected tools and manual processes.

Solution — built and supported role-aware admin interfaces, operational dashboards, filtered data views, reporting workflows, status tracking, assignment management, and the backend APIs that powered them.

React AngularJS Node.js REST APIsEF Core PostgreSQLMongoDB
P—04Performance

Multi-Layer Cache API

Problem — a data API needed a faster and more resilient read path without sending every request directly to the database.

Solution — built a production-style .NET API with cache-aside reads through in-memory cache, Redis, and PostgreSQL. Successful writes refresh both cache layers, while Docker Compose provides a reproducible local environment.

.NETRedisPostgreSQLDocker
Read path · cache-aside≈1 ms served
Hit
In-Memory Cache L1 · hot · ≈1 ms
92% of reads
miss ↓
Redis L2 · distributed · ≈5 ms
7%
miss ↓
PostgreSQL source of truth · ≈40 ms
1%
successful writes refresh both cache layers
Conversion pipeline converting
Upload API
Queue Background
Worker ×3 Isolated
Output Multi-format
report.docx → PDF68%
PDF DOCX XLSX PNG retry on failure · workspace cleanup
P—05Workflow Automation

Document Conversion Service

Problem — users needed to upload business documents, convert them into multiple formats, track progress, and retrieve the result without blocking the main application.

Solution — built an API-driven .NET service with upload and status APIs, background processing, Microsoft Office-based conversion, SignalR notifications, retry and failure handling, workspace cleanup, and isolated conversion workers that could be scaled independently.

.NET 10PostgreSQLSignalREF CoreOffice InteropBackground Processing
04 — About

A calm, dependable technical partner — not just a pair of hands.

I work best on serious, long-lived software where understanding the product matters as much as completing the next task. I think through the architecture, communicate clearly, and take ownership of the result rather than simply closing tickets.

I work across the full stack, with particular depth in backend architecture, APIs, databases, integrations, and data-intensive workflows. I care about how the entire system fits together — not only how individual features are implemented.

Clear, direct communication
Ownership from architecture to delivery
Clean, maintainable, tested code
Pragmatic problem-solving over hype
05 — Let's Talk

Let's build something reliable.

Tell me what you want to launch, improve, or repair. Share the current state, the main problem, and the outcome you need — I’ll respond with concrete technical thoughts.

Continue on Upwork  ↗
Katerina Sh · Full-Stack Engineer © 2026 · All rights reserved