Fintech, Crypto & Blockchain Architecture

Building the infrastructure
behind fintech & decentralized finance

We design and deliver secure, scalable architecture for fintech, crypto and blockchain projects — from smart contracts and token systems to DeFi platforms and presale infrastructure.

16 Years In Business
50+ Projects Delivered
100% Client Satisfaction

End-to-end blockchain solutions

From architecture design to deployment, we help crypto and fintech teams build reliable systems that scale.

Blockchain Architecture & dApps

System design for dApps — node infrastructure, layer selection, cross-chain bridges, and scalable backend architecture.

Smart Contracts

Secure smart contract development for Solana, Ethereum, EVM-compatible chains, Stellar, and custom blockchain environments.

DeFi Platforms

Decentralized exchange logic, liquidity pools, staking mechanisms, yield strategies, and governance systems.

Token Development

SPL and ERC-20/721 tokens — FoT, KYC-whitelisted, stablecoin, and RWA issuance — vesting schedules, treasury and distribution logic, and on-chain analytics.

Presale & Launch

Token and meme coin presale platforms, whitelist management, contribution tracking, and fair launch mechanisms with anti-bot protection.

Fintech Integration

Bridging traditional finance with blockchain — stablecoins, cross-border payments, payment gateways, KYC/AML flows, fiat on/off ramps, and compliant architecture.

KYC & KYB

Identity and business verification for wallets, exchanges, and fintech apps — Persona, Sumsub, Bridge.xyz, and Rain.xyz.

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Deep technical knowledge across the stack

We combine decades of software engineering with specialized blockchain expertise. Every solution is built for security, performance, and long-term maintainability.

Chains

Solana, Ethereum, Base, BSC, Polygon, Arbitrum, Stellar

Smart Contracts

Rust, Solidity, OpenZeppelin, Anchor, Foundry

Backend

Node.js, PHP/Laravel, PostgreSQL, Redis

Frontend

React, Web3.js, Ethers.js, WalletConnect, Privy

Infrastructure

AWS, Digital Ocean, Docker, CI/CD, monitoring

Security

Auditing, penetration testing, key management, multisig

From concept to mainnet

  1. 01

    Discovery

    We analyze your requirements, tokenomics, and technical constraints to define the right architecture.

  2. 02

    Architecture

    System design, smart contract specifications, and infrastructure planning before any code is written.

  3. 03

    Development

    Iterative development with testnets, code reviews, and continuous integration throughout.

  4. 04

    Launch & Support

    Mainnet deployment, monitoring setup, and ongoing maintenance to keep your systems running flawlessly.

Engineering excellence in a decentralized world

Castor is a specialized blockchain engineering studio. We help fintech and crypto startups build the technical foundation for their products — from the first whitepaper sketch to a live, production system.

With over 20 years of software development experience, we bring enterprise-grade engineering practices to the fast-moving fintech and crypto: clean code, thorough testing, and architectures designed to evolve.

Željko Kovacevic
Zeljko Kovacevic Founder & CEO

Expert software architect with a Master of Information Technology. Passionate about building secure, scalable systems — now focused on fintech, blockchain, and decentralized technologies.

Trusted by teams worldwide

“Excellent work. Zeljko demonstrated a very high level of professionalism, quickly understood our needs, and delivered flawless execution. His assistance with the client page as well as with the setup and optimization of the billing and payment methods was particularly valuable. Communication was smooth, deadlines were respected, and the overall quality of the work was outstanding. I recommend him without reservation.”

Switzerland Damien M.
CEO

“This is the second time working with Zeljko and an outstanding experience yet again. He managed to do a complex API integration of a payment gateway system with an existing, undocumented PHP platform. Great communication, flexibility and fast execution as always!”

Seychelles Antonio J.
CEO, Next Campaign

“Zeljko was an absolute pleasure to work with! He exceeded my expectations by going above and beyond to meet my requirements and even took the initiative to create comprehensive documentation for the project. I would definitely work with him again!”

United States Meme M.
Founder

“Zeljko did an exceptional job with the development of a fairly complex web app that required great skills in JavaScript, React, PHP, Laravel, AWS, SQL and API integration. I have worked with dozens of developers and he is by far the most skilled in both frontend and backend development. He is always ready to respond quickly and he can get complex tasks done fast while maintaining the great quality. Definitely recommended for all web development needs.”

Seychelles Antonio J.
CEO, Next Campaign

“Zeljko was proactive in coming up with a possible solution at an early stage, preemptively thought about possible constraints and how one could work around them above and beyond the initial job description, and was quick to iterate on the product after initial feedback and testing.”

Switzerland Mark M.
Owner

“Zeljko has been excellent. He has top tier communication and technical skills. He comes up with innovative technical solutions to solve any problems we run into. He always adheres to deadlines. I would highly recommend him for any development work.”

United States Jonathan W.
Manager

“Competent and skilled developer, excellent in communication, able to resolve all issues, I will be looking to hire him again in the future!”

Croatia Goran T.
CEO, GT Audio

“Zeljko did an amazing work on my project! He was always very reactive, and could solve every problem I encountered. I'm very grateful for all what he did on my project. Thank you sooo much!!!”

Switzerland Sebastien G.
CEO

“Highly competent developer, delivered on everything needed on both the back and the front end, excellent in communication and pleasant to work with. I can only recommend Zeljko and will be hiring him again!”

Croatia Goran T.
CEO, GT Audio

“Very fast, very good communication and a really good code! I recommend him 100%.”

Bulgaria Matthieu F.
CEO, MF Network

“Understood me (another coder), delivered on time, good communication, excellent instructions, made it easy for me.”

United Kingdom Craig
Founder

“Zeljko completed the task successfully and on time. Our collaboration went great without any hiccups. My highest recommendations!”

Serbia Dusan C.
CEO

“Zeljko was great to work with, very friendly and professional.”

United States Mony R.
CEO

“Really fast as always, a good problem solver! I recommend him 100%.”

Bulgaria Matthieu F.
CEO, MF Network

“Great collaboration with Zeljko as always! My highest recommendations!”

Serbia Dusan C.
CEO

“Great work! Very skilled — highly recommended.”

United States M. Rubin
CEO

“Second experience with Zeljko, still perfect! Thanks a lot.”

Bulgaria Matthieu F.
CEO, MF Network

“Exceptional work as always!”

Switzerland Sebastien G.
CEO

“I had the pleasure of working with Zeljko for 10 years, collaborating on lots of projects. He worked as a lead programmer and is one of the most dedicated professionals I've worked with.”

Croatia Antonija D.
Head of Sales, Ponuda Dana

Clients worldwide

Teams we’ve worked with across five continents.

  • USA
  • Brasil
  • Kenya
  • UK
  • Switzerland
  • Austria
  • Bulgaria
  • Romania
  • Croatia
  • Serbia
  • Turkey
  • Hong Kong
  • Jamaica
  • Seychelles
  • UAE
  • Cyprus
  • Marshall Islands

Let's build something together

Whether you're launching a token, building a DeFi protocol, or need blockchain architecture consulting — we'd love to hear about your project.

info@castorweb.eu

Frequently asked questions

What services does Castor provide?
Blockchain architecture, smart contract development, DeFi platforms, token development, presale and launch infrastructure, fintech integration, and KYC and KYB integration — from initial design through production deployment.
Which blockchains do you work with?
Primarily Solana and Ethereum/EVM ecosystems, with experience on Stellar and cross-chain designs. We help you choose based on your product, users, and performance needs.
Do you only consult, or do you also build?
Both. We deliver architecture and documentation, and we implement the full stack — smart contracts, backends, integrations, and user-facing applications.
How do I start a project with Castor?
Use the contact form or email info@castorweb.eu with your goals, timeline, and constraints. We respond with a practical next step — a scoping call, architecture review, or proposal.
Do you work with international clients?
Yes. We work with teams worldwide and have delivered projects across five continents. Communication is in English or Croatian.