Expert React & Next.js development for complex, data-intensive and interactive web applications — AI-powered apps, CRMs, SaaS Dashboards, User Management Systems, and API integrations.
For the last decade I have been working on various projects starting from developing Landing Pages, Marketplaces and up to Messengers, and Next.js Web Applications Builder. Eventually, I found my passion in building complex products, that are meant to simplify life and optimize business processes. Are you looking to build or improve one?
Connecting...
Real-Time Collaboration Apps
Whether your app is for real-time collaboration of distributed teams like Figma or your users need to see data updates instantly, like Binance, it comes with the similar set of challenges and require niche knowledge to leverage modern technologies and keep the app performant
This interactive canvas demonstrates the power of WebRTC and selective forwarding. Every cursor with a flag you see is a real person, exploring this space with you.
Web applications development
Interface builders
When your product needs to give users creative control — whether that's building pages, designing workflows, or configuring complex rules — off-the-shelf solutions stop working quickly. The moment users need more than a settings panel, you need a real builder: one with drag-and-drop, undo/redo, live preview, and the ability to serialise and restore user-created layouts reliably.The challenge is that builders feel deceptively simple until you're six months in and refactoring your state model. Getting the architecture right from the start — the component tree structure, the action/history stack, the rendering engine — is what separates builders that scale from ones that become unmaintainable.
MVPs
Getting to product-market fit is a process of fast, informed iteration — not a single well-planned build. The SDLC gets stripped to its essentials: short cycles, direct client involvement at every stage, and scope decisions made on signal rather than assumption.Close collaboration with stakeholders through the build — frequent demos, shared prioritisation, rapid feedback loops — is what keeps the product converging on what users actually need rather than what was planned at kickoff.
Chats and real-time communications
WebSocket architecture, WebRTC peer connections, and event-driven state synchronisation operate under constraints that set them apart from standard request-response development: message ordering guarantees, reconnection strategies, presence state at scale, and conflict resolution under concurrent writes all require deliberate design decisions.Chat products deployed at scale by teams at Harvard, the NBA, and Stanford put these constraints under real-world stress — high-concurrency events, enterprise-scale user bases, and zero tolerance for message loss.
Files processing
File processing in production involves a layered set of concerns across the full pipeline — from ingestion and transformation to storage, access control, and retrieval. Each layer introduces its own security surface and performance constraints that require deliberate handling.Signed URL strategies, concurrent upload handling, and processing pipelines that operate without blocking server resources are the decisions that have the most durable impact on how the system behaves under real load.
Productivity tools
The core engineering challenge in productivity tools is relational data integrity — tasks have owners, dependencies, deadlines, and states that all interact. Layer on RBAC or PBAC, timezone-accurate date arithmetic, and real-time conflict resolution for concurrent edits, and the data model becomes the primary determinant of product quality.Getting these foundations right — the permission model, the event architecture, the sync strategy — is what determines whether the product handles real organisational complexity or only the scenarios it was demoed with.
Chats and real-time communications
WebSocket architecture, WebRTC peer connections, and event-driven state synchronisation operate under constraints that set them apart from standard request-response development: message ordering guarantees, reconnection strategies, presence state at scale, and conflict resolution under concurrent writes all require deliberate design decisions.Chat products deployed at scale by teams at Harvard, the NBA, and Stanford put these constraints under real-world stress — high-concurrency events, enterprise-scale user bases, and zero tolerance for message loss.
Files processing
File processing in production involves a layered set of concerns across the full pipeline — from ingestion and transformation to storage, access control, and retrieval. Each layer introduces its own security surface and performance constraints that require deliberate handling.Signed URL strategies, concurrent upload handling, and processing pipelines that operate without blocking server resources are the decisions that have the most durable impact on how the system behaves under real load.
Productivity tools
The core engineering challenge in productivity tools is relational data integrity — tasks have owners, dependencies, deadlines, and states that all interact. Layer on RBAC or PBAC, timezone-accurate date arithmetic, and real-time conflict resolution for concurrent edits, and the data model becomes the primary determinant of product quality.Getting these foundations right — the permission model, the event architecture, the sync strategy — is what determines whether the product handles real organisational complexity or only the scenarios it was demoed with.
Let's connect!
Say hi at hi@levchenkod.com