I help businesses build reliable data platforms and AI-powered applications. With 10+ years of experience in SQL Server, PostgreSQL, C#, and database optimization, I develop solutions that combine high-performance databases with modern AI technologies. I can help you with: SQL query optimization and performance tuning Database design and data modeling ETL pipelines and data migration ASP.NET Core backend development AI integration using OpenAI-compatible APIs AI assistants that work with SQL databases and business documents Retrieval-Augmented Generation (RAG) Vector search with PostgreSQL (pgvector) REST APIs and backend services Stored procedures, functions, and triggers ETL and data migration SQL Server ↔ PostgreSQL ↔ Oracle migrations Power BI data preparation Building DWH (Medallion Architecture) Database troubleshooting and production support I focus on practical business solutions—whether it's optimizing a slow database, building a data platform, or integrating AI into an existing application. If you need someone who understands both databases and modern AI workflows, I'd be happy to discuss your project.

An AI & Data-Driven SaaS Developer specializing in building intelligent, multi-tenant SaaS applications powered by advanced analytics. Skilled in Power BI for interactive dashboards and data visualization to transform complex datasets into actionable insights, enabling businesses to make smarter, faster decisions.

Hi, I’m Sergey — hands-on Senior Software Engineer & former CTO who still loves writing code. What you get - Senior expertise at a starter rate. I’m brand-new to Upwork and charging less until I earn reviews, so you get top-tier skills without the boutique price tag. - Clear, friendly communication. Frequent progress notes, fast replies, zero tech-speak unless you ask for it. - Full ownership. I stay from first commit to final hand-off and keep helping until everything runs smoothly. How I can help - Back-end: Ruby / Rails, Python / FastAPI, Node.js (Express, Nest). - Front-end: React, Next.js, Vue — from quick admin dashboards to full-blown SPAs. - Data stores & performance: Design, build, or tune PostgreSQL, MySQL, Kafka, ClickHouse, Redis, MongoDB for serious scale. - AI features: LLM fine-tuning, text summarisation, image & document analysis, time-series predictions - only when they add real value. - Cloud & DevOps: AWS, GCP, Docker, Kubernetes, CI/CD pipelines that make deploys boring. Recent project wins: NOAH (Agri-insurance AI, 2023 - now) - Built a Visual-Transformer pipeline that turns multispectral satellite images into early-warning crop-health scores. - Added OCR with Detectron2 to read handwritten farm documents, boosting parsing accuracy from 78 % to 96 %. - Delivered the full stack (React + FastAPI) containerised for smooth rollout on GCP. GdeSlon (AdTech platform, CTO 2010 - 2023) - Architected an API that stays under 40 ms p95 at 300 req/s, searching through tens of millions of products. - Implemented real-time tracking & targeting logic that lifted click-through rate by 15 %. - Grew the tech team from 0 → 25 while staying hands-on with code. CTS @ Sun Microsystems (Backend lead, 2007 - 2008) - Led development of the Competency Tracking System later adopted by tens of thousands of Sun customers worldwide. - Co-invented a secure web workflow that earned a patent and became part of Sun/Oracle documentation. - Delivered Sun’s first production Ruby service, fully integrated with corporate SSO. Have a question? Message me anytime. Let’s see if I’m the right fit for your project.

Companies hire me when their data is stuck in spreadsheets and their team is spending 10–25 hours a week on manual reporting that should be automated. I build the infrastructure behind that shift: executive dashboards your team checks daily, data automation pipelines that eliminate manual work, and AI-powered workflows that handle the repetitive tasks eating into your team's time. My clients are SMBs in e-commerce, healthcare, SaaS, and professional services. ──────────────────────────────────────── WHAT I BUILD ──────────────────────────────────────── Business Intelligence & Data Visualization Custom dashboards in Power BI, Looker Studio, Metabase, and Tableau — connected to your CRM, ERP, and financial systems. Designed around the decisions your leadership actually needs to make, not just charts that look good in a demo. Self-hosted by default — your data stays on your infrastructure, not a vendor's cloud. Data Pipelines, ETL & Data Warehouse ELT pipelines using Airbyte, dbt, and ClickHouse, BigQuery, or Snowflake — ingesting data from Shopify, Stripe, QuickBooks, NetSuite, Salesforce, HubSpot, Google Analytics (GA4), and custom APIs. One recent engagement: fully automated a multi-source data pull that was costing a client 25+ hours per week in manual effort. Built with Python and SQL throughout. AI-Powered Workflows & Automation n8n and Windmill automations, model-agnostic AI agents (Ollama for private/local deployments, GPT-4, Claude, Gemini where appropriate), and LLM-assisted workflows for AP processing, anomaly detection, and automated reporting. If a task is repetitive and rule-based, it can be automated — and I'll tell you honestly when it can't. ──────────────────────────────────────── TRACK RECORD ──────────────────────────────────────── - Eliminated 25+ hours/week of manual data work for a multi-entity e-commerce brand by automating API pulls from Shopify, Stripe, and NetSuite into a centralized data warehouse using Python and SQL. - Built driver-based forecasting models — sales, margin, headcount, inventory — now used in monthly executive planning cycles across finance and operations. - Deployed real-time KPI dashboards for clients across e-commerce, healthcare, legal, and SaaS — all currently in active daily use. - Reduced reporting cycle time by 12+ hours/week using automated reporting workflows and LLM-assisted anomaly triage built in n8n. - M.Sc. in Data Science — I understand the models behind the metrics, not just the tooling on top. ──────────────────────────────────────── HOW I WORK ──────────────────────────────────────── Most of my engagements are ongoing retainers — I run and maintain the pipelines and dashboards we build together, so you're not left holding infrastructure you don't have the team to support. Every build comes with clean documentation and a Loom walkthrough. You own everything, no black boxes. ──────────────────────────────────────── Send me a brief description of your current setup and what isn't working. I'll respond with questions or a scoped proposal — typically within 24-48 hours.

Need AI integrated into a system that already works? I build production Claude/LLM backends — Tool Use, prompt caching, structured output, streaming — and the data pipelines they sit on top of. Python that ships on time, ships with tests, and runs in production, not scripts that break next week. What I build with AI: → Claude/LLM integrations — Tool Use orchestration, prompt caching (51.8% hit rate measured in production, not estimated), structured output, SSE streaming, FastAPI endpoints. Production-grade scope enforcement and cost control. → AI features inside existing apps — added Claude-powered exception detection to a client's IFRS 9 accounting app without touching the frozen calculation engine. The hard part is not the API call, it is knowing what not to break. → Workflow automation — n8n integration (cron + REST dispatch + status polling), FastAPI inference services with automated retrain workflows, Telegram and Discord bots with persistent state and error recovery. Recent work: → IFRS 9 loan accounting app in Streamlit — code hardening, UI conversion, and a Claude-powered exception detection feature. The client, a non-engineer, wrote: "Excellent at explaining technical work in plain language, even without a technical background." 5.0 stars. → Bitfinex P2P lending bot in production — multi-key architecture, watchdog with automatic recovery, 138+ hours across deployment, debugging, and daily monitoring. Running unattended. → SEC EDGAR 10-K parser for Business Development Companies — 103 companies, $1,324,753K reconciled to the audited Total Investments line, 58/58 tests passing, Docker. Also: → Quant & trading systems — signal generation, multi-timeframe funnels (ADX, EMA, Bollinger, ATR-based sizing), backtesting with look-ahead detection, exchange APIs (Binance, Bitfinex, Deribit), ClickHouse and SQLite tick storage. → Financial data engineering — SEC EDGAR filings, multi-source ETL across financial APIs, Pandas + PostgreSQL pipelines, idempotent ingestion with deduplication and audit logging. → ML & classification pipelines — fastText, scikit-learn, PyTorch feature extraction, confidence calibration. How I work: every project Dockerized, deployed on DigitalOcean (or your cloud), version-controlled, tested, documented. I check my own work before you have to — on one research project I found a look-ahead bias in my own backtest and reported it rather than shipping the number. I respond within hours, ask scoping questions before quoting, and ship on time. If something breaks after delivery, I fix it. Bilingual EN/中文 native, Taiwan-based. Available 30+ hours per week. Comfortable with US morning hours.

👋 I'm a Full-Stack Web Developer with 3+ years of experience building scalable, responsive, and secure web applications using Java, Spring, .NET Core, Angular, Next.js, and AWS. I help startups and businesses build modern web platforms, REST APIs, and custom dashboards with fast performance and clean architecture. ✅ Developed full-stack apps with user authentication, product listings, payments, and role-based accessz scalable architecture, millions of users. ✅ Built and deployed secure APIs with .NET Core and Node.js, integrated with SQL/MongoDB, Postgres ✅ Designed admin panels and internal tools for HR, e-commerce, and healthcare workflows, identity management tools, finance SAAS, AI agents. ✅ Deployed production systems using Docker, Linux, and AWS for high reliability I focus on writing clean, maintainable code following SOLID principles and scalable architecture. Whether you need a small app or a complete system, I’ll bring your idea to life with clean UI and solid backend logic. Let’s connect — I’m ready to help you build, launch, and scale!

I architect, scale, and rescue high-load Python backend systems. As an Expert-Vetted Python Architect (Top 1%), I partner with engineering teams to resolve deep performance bottlenecks in applications that have outgrown their initial architecture. With a decade of engineering experience, my work focuses on structural solutions rather than patching symptoms. I build scalable backends capable of handling severe traffic spikes, supported by rigorous database tuning and event-driven design. ENGINEERING FOCUS - High-Load Backend Architecture I design async-first FastAPI and Django services built for scale. I implement horizontal scaling, robust caching layers (Redis), and reliable message brokers (Kafka, RabbitMQ, Celery) to ensure system stability under unpredictable loads. - PostgreSQL Performance & DBA I specialize in advanced database optimization. When standard indexing is no longer sufficient, I implement table partitioning, logical replication, PgBouncer connection pooling, and complex query refactoring. My priority is redesigning data access patterns and eliminating N+1 anomalies at the ORM layer. - System Refactoring & Technical Debt I regularly audit struggling backends. I provide comprehensive profiling for memory leaks, slow queries, and I/O bottlenecks. I execute phased refactoring without halting production, delivering fully tested, documented code integrated into your CI/CD pipelines. • Production-Grade AI Integration Integrating OpenAI/Anthropic APIs into backend workflows. I build fault-tolerant RAG pipelines using pgvector, ensuring strict rate-limiting, cost-monitoring per token, and fallback mechanisms for predictable enterprise use. RECENT INFRASTRUCTURE WINS - Resolved critical database lockups in a monolithic Django app by implementing PgBouncer connection pooling and refactoring ORM queries, reducing required compute infrastructure by over 40%; - Redesigned data access patterns on a 2.5B+ row PostgreSQL table via declarative partitioning and materialized views, dropping complex analytical query latency from ~35s to under 250ms; - Migrated a high-traffic synchronous Django API to async FastAPI, reducing average response times by 70% with zero downtime. Due to the nature of enterprise work, client names are strictly confidential. I am happy to discuss specific architectural patterns and system designs during an interview. Tech Stack: Python, FastAPI, Django, PostgreSQL, ClickHouse, Redis, RabbitMQ, Kafka, Celery, Docker, Kubernetes, AWS, GCP. I am currently accepting select engineering projects. Let's schedule a technical sync to discuss your current architectural bottlenecks.

Most backend issues in production systems are not caused by technology - they come from early architecture decisions, fragile integrations, or systems that were never designed to scale. I help startups and product teams design and build reliable backend systems that hold up in production, not just prototypes that work in demos. Over the past 4+ years, I’ve worked on backend systems powering real products - designing APIs, data architectures, and event-driven systems using Node.js and Go. 𝙋𝙧𝙤𝙫𝙚𝙣 𝙩𝙧𝙖𝙘𝙠 𝙧𝙚𝙘𝙤𝙧𝙙 ・1200+ hours on Upwork delivering high-end development services ・100% Job Success Score (JSS) ・4+ Years in Software Engineering with a deep focus on Node.js & Go 𝙒𝙝𝙖𝙩 𝙄 𝙘𝙖𝙣 𝙝𝙚𝙡𝙥 𝙮𝙤𝙪 𝙗𝙪𝙞𝙡𝙙 Backend & API Development ・REST, GraphQL, and tRPC APIs ・Node.js frameworks: Express, Fastify, NestJS ・Clean API contracts and versioning ・Third-party API Database & Data Architecture ・PostgreSQL, MongoDB, ClickHouse ・Schema design and migrations ・Query optimization ・ORMs: TypeORM, Drizzle, Sequelize, Mongoose Event-Driven & Real-Time Systems ・Message queues with NATS and BullMQ ・Real-time communication via WebSockets or SocketIO ・Event-driven architectures for scalable services Data Acquisition & Automation ・API reverse engineering ・Web scraping systems ・Automation using Puppeteer and Playwright 𝙇𝙚𝙩’𝙨 𝙩𝙖𝙡𝙠 If you're building a system that needs to scale, remain maintainable, and survive production growth, I’d be happy to discuss your project. 𝘾𝙤𝙧𝙚 𝙏𝙚𝙘𝙝𝙣𝙤𝙡𝙤𝙜𝙞𝙚𝙨 Node.js • TypeScript • Go Express • Fastify • NestJS PostgreSQL • MongoDB • ClickHouse NATS • BullMQ • WebSockets • SocketIO TypeORM • Drizzle • Sequelize • Mongoose Puppeteer • Playwright

I have been managing development teams for over 12 years with successful agile development methodologies and I enjoy to automate processes.

Summary of Qualifications: • Expert in MS PowerBI, Netsuite Orcale and Fishbowl Inventory Report Customization • 20 years of accumulated talent and professional experience in Data Analysis, NodeJS, PHP, Java, MySQL, Oracle, MS SQL, Firebird and Jasper iReport • Excellent in creating stored procedures, functions, view and triggers • Skilled in hardware operating systems and network procedures • Exceptional history with content management relational databases systems and web development and web services • Extensive knowledge of CSS/HTML jQuery, Joomla, WordPress, etc. • Strong analytical skills and attention to detail. • Reliable, self-motivated and with a strong sense of integrity • Perform effectively and efficiently even under pressure • Relate well with others and able to build and maintain relationship • Creative mindset, and ability to make complex decisions and work on fast-paced, team-oriented environment while handling multiple priorities. Experience: Global Agile Development Inc, Florida USA, MySQL Expert Database Administrator Davao del Norte State College, Philippines • Currently working as IT Instructor and teach the following subject areas: o Java and PHP programming o Database • Developed the following application program o Enrolment System o Student Information System