Marcin Stempniewicz

Marcin Stempniewicz is the CTO of KW Rental Investments and the architect of CommunitySync, the platform this community runs on. He builds the systems that let an agent turn a rental lead into a forecast, a listing, a shareable report and a closed deal without leaving one place.

Building platforms for communities

Marcin, together with Jason Ross, designed CommunitySync as a multi-tenant platform from the ground up: every community gets its own brand, its own domain, its own feature set and its own member portal, all served from one codebase. For KW Rental Investments that means the Rental Forecast and Cost Estimate engines, the opportunity listings and lead inbox, the education playbook, the marketing library, the agent directory you are reading now, and a website builder that gives every agent a personal site under the community's domain. The platform now hosts communities well outside real estate, from an  Underwater 3D Academy to a furniture visual-commerce company, which is the real test of whether a "community platform" is actually general.

His design rule is simple: the agent's job comes first, the system's cleverness last. A report has to be identical every time it is generated. A shared link has to work on any host. A member should never see another community's data, and that guarantee is enforced and tested, not assumed.

Rendering at scale

Before CommunitySync, Marcin co-founded Ar-range, a visual-commerce platform for furniture brands. It renders every product variant a brand sells, millions of images from a single 3D source, with a catalog engine, a 3D configurator and AI search on top. The same batch-rendering and automation discipline runs through everything he builds: pipelines that produce the same output on every run and scale without a human in the loop.

Exploration and speaking

Outside the codebase Marcin is a TDI Full Cave diver, technical wreck diver and 3D artist based in Poznań, Poland. He founded the Submerged Foundation to document flooded mines, caves and wrecks as accurate, explorable 3D models. His flagship project, the Maria Concordia flooded magnesite mine, supported by the XDEEP Exploration Support Program, took hundreds of hours underwater across four levels and a 40-metre shaft and produced a single coherent model of the mile-long site. He collaborates with Poland's National Maritime Museum on the digital documentation of wrecks and founded U3DA, an academy that teaches divers and marine archaeologists to turn their scans into cinematic 3D.

He has presented at Hidden Earth (UK), the NSS Convention (West Virginia 2024, Tennessee 2025), Baltictech and Dive Expo Belgium 2025, on how accurate 3D documentation changes cartography and dive planning in overhead environments, and speaks at technology events on rendering automation and building multi-tenant platforms. His work has appeared in InDepth (GUE), XDEEP ESP, divers24 and Podcast Spod Wody.

"The raw scan is not the product," Marcin says. "The story people can actually use is." It is the same principle behind every tool on this platform: the data is not the deliverable, the decision an agent can make with it is.