Ecommerce agencies divide into firms that build and maintain the store and firms that grow its revenue, and a minority that genuinely do both. The distinction matters because a brilliant build team will not improve conversion or acquisition, and a strong growth team cannot fix a store that will not do what it is asked.
Build and growth are different companies
Build work is platform implementation, theme development, integrations with inventory and fulfilment, and performance. Growth work is acquisition, merchandising, conversion, retention and lifetime value. Some firms do both well. Many present as full service and are strong at one, which shows up three months in when the other half stalls.
The platform decision constrains everything
Hosted platforms limit customisation and remove maintenance. Open platforms allow anything and require someone to own upgrades and security. Headless builds add flexibility and cost. The right choice depends on catalogue complexity, integrations and who will maintain it, not on what the agency prefers to build in.
Where growth actually comes from
Usually retention and merchandising before acquisition. Repeat purchase rate, average order value, email and lifecycle programmes, and the conversion path on the pages that already receive traffic. Agencies that lead with acquisition are selling the most visible lever, which is rarely the cheapest one available.
What to own
The store, the domain, the customer data, the email platform, the advertising accounts and the code. Ecommerce concentrates more critical assets in supplier hands than most projects, and disentangling a store from an agency that hosts, builds and markets it is genuinely difficult. Settle it before the build.
Questions people ask about e-commerce agency
Should one agency build and grow the store?
It can work and it concentrates risk. Many merchants use a build partner and a separate growth team, with clear ownership of the codebase and a way for both to work without blocking each other.
How do I judge an ecommerce agency?
Ask for stores they built or grew that are still trading, and what the merchant would say about the handover. Longevity after the project is more informative than launch screenshots.
What is the most common build mistake?
Building for a catalogue and a process that will change, and doing so on a customised stack only that agency can maintain. Simple and standard is usually cheaper over five years.
Where should a small merchant start?
With the conversion path and retention on what already exists, before buying more traffic. Most small stores can improve revenue without increasing acquisition spend at all.