Building an Ecommerce Store on Spree: From Monolith to Headless

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
        price * 0.9
      elsif quantity >= 5
        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.