Custom eCommerce Development
Sometimes the product does not fit a cart. Rentals with availability windows, marketplaces with per-vendor payouts, industrial configurators where price depends on a dozen inputs, memberships that unlock entitlements rather than ship a box — these bend platforms until the workarounds cost more than the build. Zelpex builds commerce systems from scratch for those cases, and only those cases.
A custom build is the most expensive option and usually the wrong one. Before starting, we test whether a platform plus a well-scoped extension gets you ninety per cent of the way, because that route is faster, cheaper and easier to hire for. When the answer is genuinely no, building it properly beats spending years fighting software that disagrees with your business.
- Rental, booking and availability models with time-based inventory
- Marketplaces: vendor onboarding, split payments, commission and payouts
- Configure-price-quote flows where price is calculated, not looked up
- Entitlement and membership models that grant access rather than ship goods
Try to avoid the build
We start by looking for the platform-shaped answer. If Shopify, BigCommerce, Adobe Commerce or Medusa can carry the model with reasonable extension, that is our recommendation even though it is the smaller engagement.
Model the domain
We write down the rules that make your business unusual — how availability works, how price is derived, who gets paid what — as explicit, testable logic rather than assumptions living in someone's head.
Build the risky part first
Whatever is most likely to be wrong gets built and tested against real data early: the pricing engine, the availability calendar, the payout maths. Discovering it later is what turns these projects into overruns.
Make it operable
Admin tooling, audit trails, monitoring and runbooks are part of the build, not a phase two. A custom system without them becomes dependent on whoever wrote it, and that dependency is a liability for you.
What founders and product teams ask us
A useful test: list the five things a platform would force you to work around. If they are cosmetic or affect the admin only, use the platform. If they touch how money is calculated, how inventory behaves over time, or who is party to a transaction, a platform will keep fighting you and custom starts to make sense.
We integrate established providers rather than building those ourselves — Stripe or Adyen for payments, a tax engine for VAT and sales tax, an established KYC provider where marketplaces require it. Custom should apply to your business logic, never to PCI scope or tax rules.
That is the fair thing to worry about, and the reason we care about documentation, conventional stacks and test coverage. We build on mainstream technology precisely so another team can pick it up. If you want to move the work in-house later, we will help with the handover rather than making it difficult.
How we scope custom builds
In slices with working software at the end of each, not as one long build that reveals itself at the end.
Custom commerce is where budgets most often overrun, almost always because the hardest rule was left until late. We invert that deliberately: the pricing engine, the availability model or the payout logic gets built and tested against real data first, while there is still room to change direction cheaply.
Thinking about a project like this?
Tell us what you are building and what is getting in the way. You will get an honest read on scope, approach, and whether we are the right team for it — including when the answer is that you do not need us.
Services that pair well with custom builds
Adobe Commerce Integration
Enterprise-grade e-commerce solutions with Adobe Commerce (Magento). Full integration, customization, and ongoing support for scalable online stores.
BigCommerce Development
Build and scale your online store with BigCommerce. Custom themes, integrations, and performance optimization for growing businesses.
Shopify Commerce Development
Custom Shopify stores, theme development, and app integrations. From startups to enterprise with Shopify Plus solutions.