Real engagements with named clients where the facts are public, and what they say about working with me.
Took over a prototype stuck after two years of outside development, re-architected it on AWS in six months - then stayed the exclusive engineering partner for eight years. Owned bank connectivity end to end: Plaid Link and re-authentication, Dwolla funding sources, instant and manual verification, ACH transfers, merchant onboarding and risk state.
A versioned external API (v1/v2) with API-key auth and a per-app audit log, so other products could open bank accounts, move money and bill their own customers through the platform - documented, tested end to end, and shipped with a reference client.
Web and product engineering for DeFi protocols - liquid staking, governance-incentive marketplaces, tokenized yield and NFT lending - plus a web3 security firm. Interfaces on Next.js with ethers.js and web3.js, wallet and DeFi integrations, on-chain data indexing and node operation behind them.
Recording sales the platform itself never publishes: private GraphQL operations captured from the web client, authenticated browser sessions, adaptive rate limiting with 429 backoff, hundreds of concurrent live streams inside a fixed request budget - plus a comps API and a human-review app on top of a Postgres record that keeps the evidence for every fact.
A 17-year client engagement that became one of AEO Content's first case studies: AI-visibility score 33 to 90 after implementing our optimization playbook.
Built and ran the custom platform behind SINGER22, a 10,000+ SKU fashion retailer. When that chapter closed, helped the same owner transform the business into fine-mineral brand 22sgems.com - new store, gallery, and an AI-narrated video catalogue publishing itself on autopilot.
17 data collectors across regulatory, court and procurement sources - SEC EDGAR full-text search, CourtListener, SAM.gov, Congress and regulator feeds - with canonical-hash dedup, per-source health checks, AI scoring and a daily brief. From idea to production in weeks.
My own products and the companies where I run the technology. AEO Content is where I am CTO today, AdPal where I was CTO in 2025; MarkosWeb is mine and runs without daily attention.
The first AI Engine Optimization platform, architected and built end to end: TypeScript monorepo with four apps, containerized crawl and audit workers, Postgres, Stripe, an MCP server, a Chrome extension and a WordPress plugin in the official directory. Audits how a site is seen by ChatGPT, Claude, Perplexity and Google AI Overviews.
My own crawl-and-data infrastructure: a domain registry with agentic-readiness scoring and a radar tracking 20,000+ accelerator companies. Collectors, dedup, scoring and a weekly digest that publishes itself - the same pipeline discipline I bring to client data work.
AI chatbot and lifecycle-engagement platform for B2B SaaS and fintech: multi-tenant RAG over customer knowledge bases, vector search, OAuth-connected CRM and ad-platform pipelines. Its architecture lessons went straight into AEO Content.
Delivered through Data Subsystems, my consultancy - the engagements above are the ones with public detail, these are the rest of the field. Some clients were early-stage startups that have since shut down or been absorbed elsewhere; where the site is gone I say so rather than link a dead page. The engineering happened either way.
Great long-term relationship. DataSub has been working with Seamless Chex for over 5 years now. They have great work ethic and provide a full stack team with strong frontend skills as well as backend development. They can work with a variety of tools and software to get the job done and their expertise has allowed for us to scale and provide our clients with a wide range of features and solutions. Alex is an exceptional team lead whom I trust implicitly. I would highly recommend.
I've been working with DataSub for over a decade now. They've built a custom PHP/Javascript e-commerce website singer22.com for me and supported it throughout the years. A year ago or so they also helped me move to Shopify platform using custom integrations and have been maintaining the store ever since. Passionate company with thorough knowledge in software engineering from inside and out, as well profound understanding of Google Ads.…