Building an Ecommerce Store on Spree: From Monolith to Headless

A client asked to add a "buy 3, get the 4th free" promo with order history validation. In Shopify, this would require a third-party app with a separate subscription; in Spree — 50 lines of a decorator. Spree Commerce is an open-source Rails Engine we use for projects requiring deep customization. In this article, we'll show how to set up monolith or headless architecture and cover real examples.

Why Choose Spree: Monolith or Headless?

Spree embeds into a Rails application as an Engine and shares the same database. Starting from version 4.3, headless mode via REST API v2 allows using Spree as a backend for React/Vue frontends. This suits both simple server-rendered stores and complex SPAs. Let's compare.

How to Set Up Spree for Your Project?

Environment setup includes installing required gems and running generators. Standard installation: add gems, run generators, migrate database. Common pitfalls: incorrect database config or gem version conflicts.

# Gemfile gem 'spree', '~> 4.10' gem 'spree_auth_devise', '~> 4.6' gem 'spree_gateway', '~> 3.10' gem 'spree_backend', '~> 4.10' gem 'spree_sample', '~> 4.10' # sample data # For headless: gem 'spree_api', '~> 4.10' 

bundle install bin/rails g spree:install bin/rails g spree:auth:install bin/rails db:migrate bin/rails db:seed 

After installation, you get:

• /admin — admin panel
• /api/v2/storefront — REST API for frontend
• / — classic storefront (if spree_frontend is installed)

Spree Data Model

Spree's database revolves around key entities: stores (multi-store support), categories (nested via ancestry), products with variants (SKU, price, options), orders with line items, payments and shipments, users.

Spree::Store ├── Spree::Taxon (categories via ancestry) ├── Spree::Product │ ├── Spree::Variant │ ├── Spree::Price │ └── Spree::Image ├── Spree::Order │ ├── Spree::LineItem │ ├── Spree::Payment │ └── Spree::Shipment └── Spree::User (via spree_auth_devise) 

Building a Headless Store with Next.js and Spree API

For headless projects, we use @spree/storefront-api-v2-sdk and work via REST API. In one project, we replaced the monolith storefront with Next.js 14 and ISR, achieving LCP under 0.8 seconds — a significant improvement in Core Web Vitals. React Server Components allow fast server-side rendering of product pages.

// lib/spreeClient.ts import { makeClient } from "@spree/storefront-api-v2-sdk"; export const client = makeClient({ host: process.env.NEXT_PUBLIC_SPREE_URL! }); // Fetch products const products = await client.products.list( { include: "default_variant,images,taxons", filter: { taxons: taxonId } }, { sort: "name", page: 1, per_page: 24 } ); // Create cart const cart = await client.cart.create(); const orderToken = cart.success().data.attributes.token; await client.cart.addItem({ orderToken }, { variant_id: variantId, quantity: 1 }); 

Customizing Business Logic Without Forking

Spree uses the decorator pattern: we add methods and associations in a module that is mixed into the model. This extends functionality without touching the core.

# app/models/spree/product_decorator.rb module Spree module ProductDecorator def self.prepended(base) base.has_many :bundle_parts, class_name: "Spree::BundlePart", foreign_key: :bundle_product_id end def bundle? bundle_parts.any? end def effective_price_for(quantity) if quantity >= 10 then price * 0.9 elsif quantity >= 5 then price * 0.95 else price; end end end end Spree::Product.prepend(Spree::ProductDecorator) 

For promotions, use the built-in Spree::Promotion system. For example, a "15% off orders over 2000 rubles" rule:

promotion = Spree::Promotion.create!( name: "Summer 15% discount", code: "SUMMER15", starts_at: Date.today, expires_at: 3.months.from_now, usage_limit: 1000 ) promotion.actions.create!( type: "Spree::Promotion::Actions::CreateAdjustment", calculator: Spree::Calculator::FlatPercentItemTotal.create!(preferred_flat_percent: 15.0) ) promotion.rules.create!( type: "Spree::Promotion::Rules::ItemTotal", preferred_operator: "gte", preferred_amount: 2000.0 ) 

This flexibility allows complex promos without extra plugins.

What's Included in the Work: Full Development Cycle

We offer turnkey development. Project stages:

The result includes: API documentation, repository and server access, client team training, 30-day warranty on bugs. Our engineers have 10+ commercial Spree projects.

Payment Integration and Multi-Currency

spree_gateway provides ready adapters for Stripe, Braintree, PayPal. For YooKassa or Tinkoff, we write a custom gateway (implementing Spree::Gateway interface). Multi-currency is configured via store attributes: set supported_currencies and supported_locales. Prices are tied to the variant's currency.

Common Mistakes When Starting with Spree

• Not using decorators — editing core Spree directly makes updates impossible.
• Forgetting N+1 queries in API — always include include in requests.
• Ignoring admin panel performance — for large catalogs, Elasticsearch is needed.
• Not setting up caching — Redis is mandatory for production. Without it, the store slows down with 1000+ products.

How to Choose Between Monolith and Headless?

If your team is strong in Rails and you need a typical store, go with monolith — it's faster to start. If you plan a mobile app, complex frontend, or high load, headless offers flexibility but requires more development resources. Order Spree store development — we will contact you within a day. Get a consultation via the form on the website or in messengers.