@flowglad/server - Flowglad Docs

Overview

The Server SDK is the core package for server-side Flowglad integration. It provides the FlowgladServer class that handles all billing operations, customer management, and API communication with Flowglad.

Installation

npm install @flowglad/server

Installation

npm install @flowglad/server

Quick Start

1. Set Up Environment Variables

.env

FLOWGLAD_SECRET_KEY="sk_test_..."

2. Create a FlowgladServer Factory Function

import { FlowgladServer } from '@flowglad/server'

export const flowglad = (customerExternalId: string) => {
  // customerExternalId is the ID from YOUR app's database, NOT Flowglad's customer ID
  return new FlowgladServer({
    customerExternalId,
    getCustomerDetails: async (customerExternalId) => {
      // Fetch customer details from YOUR database using YOUR app's ID
      const user = await db.users.findOne({ id: customerExternalId })
      if (!user) {
        throw new Error('Customer not found')
      }
      return {
        email: user.email,
        name: user.name,
      }
    },
  })
}

// Usage:
// Pass YOUR app's user/organization ID, not Flowglad's customer ID
const billing = await flowglad(userId).getBilling()

Important: customerExternalId is the ID from your app’s database (e.g., user.id or organization.id), not Flowglad’s customer ID.B2C apps: Pass user.id as customerExternalId
B2B apps: Pass organization.id or team.id as customerExternalId

3. Mount Flowglad Route Handler

Create a route handler to handle Flowglad API requests from your frontend. The Server SDK provides route handler constructors that enable your client to communicate with your server, allowing you to load billing and feature access data via the useBilling hook on your frontend. It should handle requests at “/api/flowglad/…“

Next.js App Router
Next.js Pages Router
Express
Other Frameworks

app/api/flowglad/[...path]/route.ts

import { nextRouteHandler } from '@flowglad/nextjs/server'
import { flowglad } from '@/lib/flowglad'
import { customerIdFromRequest } from '@/lib/auth'

export const { GET, POST } = nextRouteHandler({
  flowglad,
  getCustomerExternalId: async (req) => {
    const externalId = await customerIdFromRequest(req)
    if (!externalId) {
      throw new Error('Unable to determine customer external ID')
    }
    return externalId
  },
})

pages/api/flowglad/[...path].ts

import { pagesRouteHandler } from '@flowglad/nextjs/server'
import { flowglad } from '@/lib/flowglad'
import { customerIdFromRequest } from '@/lib/auth'

export default pagesRouteHandler({
  flowglad,
  getCustomerExternalId: async (req) => {
    const externalId = await customerIdFromRequest(req)
    if (!externalId) {
      throw new Error('Unable to determine customer external ID')
    }
    return externalId
  },
})

server.ts

import express from 'express'
import { expressRouter } from '@flowglad/server/express'
import { flowglad } from './lib/flowglad'
import { customerIdFromRequest } from './lib/auth'

const app = express()

app.use(
  '/api/flowglad',
  expressRouter({
    flowglad,
    getCustomerExternalId: async (req) => {
      const externalId = await customerIdFromRequest(req)
      if (!externalId) {
        throw new Error('Unable to determine customer external ID')
      }
      return externalId
    },
  })
)

server.ts

import { requestHandler } from '@flowglad/server'
import { flowglad } from './lib/flowglad'
import { customerIdFromRequest } from './lib/auth'
import type { HTTPMethod } from '@flowglad/shared'

const flowgladHandler = requestHandler({
  flowglad,
  getCustomerExternalId: async (req) => {
    const externalId = await customerIdFromRequest(req)
    if (!externalId) {
      throw new Error('Unable to determine customer external ID')
    }
    return externalId
  },
})

// Example: Hono, Cloudflare Workers, Elysia, etc.
// Adapt this pattern to your framework
async function handleFlowgladRequest(request: Request): Promise<Response> {
  const url = new URL(request.url)
  const path = url.pathname
    .replace('/api/flowglad/', '')
    .split('/')
    .filter((segment) => segment !== '')

  const result = await flowgladHandler(
    {
      path,
      method: request.method as HTTPMethod,
      query:
        request.method === 'GET'
          ? Object.fromEntries(url.searchParams)
          : undefined,
      body:
        request.method !== 'GET'
          ? await request.json().catch(() => ({}))
          : undefined,
    },
    request
  )

  return Response.json(
    {
      error: result.error,
      data: result.data,
    },
    {
      status: result.status,
    }
  )
}

4. Call Server Methods

// Fetch billing details (customers, subscriptions, invoices, etc.)
// Pass YOUR app's user/organization ID, not Flowglad's customer ID
const billing = await flowglad(userId).getBilling()

// Ensure the Flowglad customer exists
const customer = await flowglad(userId).findOrCreateCustomer()

// Create a hosted checkout session
const checkoutSession = await flowglad(userId).createCheckoutSession({
  priceSlug: 'pro_plan',
  successUrl: 'https://example.com/success',
  cancelUrl: 'https://example.com/cancel',
})

// Check feature access for gating premium functionality
const hasPremium = billing.checkFeatureAccess('premium_feature')

// Record metered usage with price (for billing)
await flowglad(userId).createUsageEvent({
  amount: 1,
  priceSlug: 'usage_price_slug',
  subscriptionId: 'subscription_id',
  transactionId: 'idempotency-key',
})

// Record metered usage without price (for tracking only)
await flowglad(userId).createUsageEvent({
  amount: 1,
  usageMeterSlug: 'api_calls',
  subscriptionId: 'subscription_id',
  transactionId: 'idempotency-key',
})

Key Features

Customer Management: Find or create customers automatically
Subscriptions: Create, update, and cancel subscriptions
Checkout Sessions: Generate checkout URLs for payments
Feature Access: Check customer access to features
Usage Tracking: Record usage events and track usage credit grants in real time
Invoices: Retrieve and manage invoices
Payment Methods: Handle customer payment methods
Pricing Model: Access your pricing model with products, prices, and features

API Reference

Constructor

new FlowgladServer(options: FlowgladServerOptions)

Options

See types.ts for more details.

type FlowgladServerOptions = ScopedFlowgladServerParams

interface ScopedFlowgladServerParams {
  /**
   * The customer ID from YOUR app's database (e.g., user.id or organization.id).
   * This is NOT Flowglad's customer ID—Flowglad uses this external ID to identify
   * and create customers in its system.
   * 
   * For B2C apps: Use your user.id
   * For B2B apps: Use your organization.id or team.id
   */
  customerExternalId: string
  baseURL?: string
  apiKey?: string
  /**
   * Handler to retrieve customer details from your database.
   *
   * This function is called when attempting to create a customer record in Flowglad
   * for a customer that doesn't yet exist. Implement this to fetch the customer's
   * name and email from your database based on their customer ID.
   *
   * @param customerExternalId - The external customer ID from YOUR system (not Flowglad's)
   * @returns Promise resolving to an object containing the customer's name and email
   */
  getCustomerDetails: (customerExternalId: string) => Promise<{
    name: string
    email: string
  }>
}

Customer Methods

`findOrCreateCustomer()`

Find an existing Flowglad customer associated with the current requesting customer (per your app’s authentication) or create a new one if none is found.

// Pass YOUR app's user/organization ID, not Flowglad's customer ID
const customer = await flowglad(userId).findOrCreateCustomer()

Billing Methods

`getBilling()`

Get comprehensive billing information for the customer, including helper functions like checkFeatureAccess, checkUsageBalance, getProduct, and getPrice.

// Pass YOUR app's user/organization ID, not Flowglad's customer ID
const billing = await flowglad(userId).getBilling()
const hasPremium = billing.checkFeatureAccess('premium_feature')
const invoiceCount = billing.invoices.length

`getPricingModel()`

Get the default pricing model with products, prices, and features.

// Pass YOUR app's user/organization ID, not Flowglad's customer ID
const pricingModel = await flowglad(userId).getPricingModel()
// Returns products, prices, and features available for purchase

Subscription Methods

`createSubscription`

Create a new subscription for the customer.

// Pass YOUR app's user/organization ID, not Flowglad's customer ID
const subscription = await flowglad(userId).createSubscription({
  priceSlug: 'pro_plan',
  metadata: {
    source: 'upgrade_flow',
  },
})

Parameters:

type CreateSubscriptionParams = {
  customerId: string
  /**
   * Must specify either priceSlug or priceId
   * Slug is encouraged over Id
   */
  priceSlug?: string
  priceId?: string
  /**
   * Quantity of the subscription items.
   * @default 1
   */
  quantity?: number
  startDate?: string
  /**
   * Epoch time in milliseconds of when the trial ends. If not provided, defaults to startDate + the associated price's trialPeriodDays
   */
  trialEnd?: number
  metadata?: Record<string, unknown>
  name?: string
  backupPaymentMethodId?: string
  defaultPaymentMethodId?: string
  interval?: 'day' | 'week' | 'month' | 'year'
  intervalCount?: number
}

`cancelSubscription`

Cancel an existing subscription.

// Pass YOUR app's user/organization ID, not Flowglad's customer ID
const canceledSubscription = await flowglad(userId).cancelSubscription({
  id: 'sub_123',
  cancellation: {
    timing: 'at_end_of_current_billing_period',
  },
})

Parameters:

type CancelSubscriptionParams = {
  id: string
  cancellation:
    | { timing: 'at_end_of_current_billing_period' }
    | { timing: 'immediately' }
}

`uncancelSubscription`

Reverse a scheduled subscription cancellation.

// Pass YOUR app's user/organization ID, not Flowglad's customer ID
const subscription = await flowglad(userId).uncancelSubscription({
  id: 'sub_123',
})

Parameters:

type UncancelSubscriptionParams = {
  id: string
}

Behavior:

If the subscription is not scheduled to cancel, the method will silently succeed without uncanceling (idempotent)
If the subscription is in a terminal state (e.g., canceled), the method will silently succeed without uncanceling
Only subscriptions in cancellation_scheduled status will have their cancellation reversed
For paid subscriptions: throws error if no payment method exists

What happens:

Status reverts to active (or trialing if still in trial period)
The cancelScheduledAt field is cleared
Billing periods marked as scheduled_to_cancel are restored
Any aborted billing runs are rescheduled

Checkout Methods

`createCheckoutSession`

Create a checkout session for payments.

// Pass YOUR app's user/organization ID, not Flowglad's customer ID
const checkoutSession = await flowglad(userId).createCheckoutSession({
  priceSlug: 'pro_plan',
  successUrl: 'https://example.com/success',
  cancelUrl: 'https://example.com/cancel',
  outputMetadata: {
    campaign: 'summer_sale',
  },
})

// Redirect user to checkoutSession.url

Parameters:

type CreateProductCheckoutSessionParams = {
  /*
   * Must specify either priceSlug or priceId
   * Slug is encouraged over Id
   */
  priceSlug?: string
  priceId?: string
  successUrl: string
  cancelUrl: string
  quantity?: number
  outputMetadata?: Record<string, string>
  outputName?: string
}

`createAddPaymentMethodCheckoutSession`

Create a checkout session that collects a payment method for the current customer.

// Pass YOUR app's user/organization ID, not Flowglad's customer ID
const session = await flowglad(userId).createAddPaymentMethodCheckoutSession({
  successUrl: 'https://example.com/payment-methods/success',
  cancelUrl: 'https://example.com/payment-methods/cancel',
  targetSubscriptionId: 'sub_123', // optional
})

`createActivateSubscriptionCheckoutSession`

Create a checkout session that activates a provisioning or imported subscription.

// Pass YOUR app's user/organization ID, not Flowglad's customer ID
const activationSession =
  await flowglad(userId).createActivateSubscriptionCheckoutSession({
    targetSubscriptionId: 'sub_123', // optional, attaches the paymentMethod to the subscription for future payments,
    successUrl: 'https://example.com/subscriptions/success',
    cancelUrl: 'https://example.com/subscriptions/cancel',
  })

Customer Updates

`updateCustomer`

Update the stored customer record in Flowglad.

// Pass YOUR app's user/organization ID, not Flowglad's customer ID
await flowglad(userId).updateCustomer({
  customer: {
    id: 'cust_abc',
    name: 'New Name',
    email: '[email protected]',
  },
})

Feature Access Methods

`checkFeatureAccess`

Check if the customer has access to a specific feature.

// Pass YOUR app's user/organization ID, not Flowglad's customer ID
const billing = await flowglad(userId).getBilling()
const hasAccess = billing.checkFeatureAccess('advanced_analytics')

if (hasAccess) {
  // Grant access to feature
}

Usage Tracking Methods

`createUsageEvent`

Record a usage event for metered billing. You can create usage events with either a price (for tracking usage with billing) or a usage meter (for tracking usage without billing).

// Pass YOUR app's user/organization ID, not Flowglad's customer ID

// Example: With price (for tracking usage with billing)
const usageEvent = await flowglad(userId).createUsageEvent({
  amount: 125,
  priceSlug: 'price_usage_meter',
  subscriptionId: 'sub_123',
  transactionId: 'txn_unique',
  usageDate: Date.now(),
  properties: {
    endpoint: '/api/data',
  },
})

// Example: With usage meter (for tracking usage without billing)
const usageEvent = await flowglad(userId).createUsageEvent({
  amount: 125,
  usageMeterSlug: 'api_calls',
  subscriptionId: 'sub_123',
  transactionId: 'txn_unique',
  usageDate: Date.now(),
  properties: {
    endpoint: '/api/data',
  },
})

Parameters:

type CreateUsageEventParams = 
  {
    amount: number
    /**
     * Must specify exactly one of:
     * - priceSlug or priceId (for billing)
     * - usageMeterSlug or usageMeterId (for tracking usage without billing)
     * Slug is encouraged over Id
     */
    priceSlug?: string
    priceId?: string
    usageMeterSlug?: string
    usageMeterId?: string
    subscriptionId: string
    transactionId: string
    usageDate?: number
    properties?: Record<string, unknown>
  }

Common Patterns

Feature Gating Middleware

import { FlowgladServer } from '@flowglad/server'
import { db } from './db'

// Factory function to create scoped instance
function getFlowgladServer(customerExternalId: string) {
  return new FlowgladServer({
    customerExternalId,
    getCustomerDetails: async (id) => {
      const user = await db.users.findOne({ id })
      return { name: user.name, email: user.email }
    },
  })
}

export function requireFeature(featureSlug: string) {
  return async (req, res, next) => {
    try {
      const userId = req.user?.id
      if (!userId) {
        return res.status(401).json({ error: 'Unauthorized' })
      }

      const billing = await flowglad(userId).getBilling()
      const hasAccess = billing.checkFeatureAccess(featureSlug)

      if (!hasAccess) {
        return res.status(403).json({
          error: 'Feature not available',
          upgradeUrl: '/pricing',
        })
      }

      next()
    } catch (error) {
      next(error)
    }
  }
}

// Usage
app.get('/api/premium-endpoint', requireFeature('premium_feature'), (req, res) => {
  res.json({ data: 'premium data' })
})

Usage Metering

// Example: Track usage with price
export async function trackAPIUsage(endpoint: string, customerExternalId: string) {
  // customerExternalId is the ID from YOUR app's database, NOT Flowglad's customer ID
  await flowglad(customerExternalId).createUsageEvent({
    priceSlug: 'price_usage_api_calls',
    subscriptionId: 'sub_current',
    amount: 1,
    transactionId: `api_call_${Date.now()}_${endpoint}`,
    properties: {
      endpoint,
    },
  })
}

// Example: Track usage without price (for tracking usage without billing)
export async function trackAPIUsageNoBilling(endpoint: string, customerExternalId: string) {
  // customerExternalId is the ID from YOUR app's database, NOT Flowglad's customer ID
  await flowglad(customerExternalId).createUsageEvent({
    usageMeterSlug: 'api_calls',
    subscriptionId: 'sub_current',
    amount: 1,
    transactionId: `api_call_${Date.now()}_${endpoint}`,
    properties: {
      endpoint,
    },
  })
}

// Usage
app.get('/api/data', async (req, res) => {
  const userId = await getUserIdFromRequest(req)
  await trackAPIUsage('/api/data', userId)
  res.json({ data: 'response' })
})

Customer Portal Generation

export async function getCustomerPortalData(customerExternalId: string) {
  // customerExternalId is the ID from YOUR app's database, NOT Flowglad's customer ID
  const billing = await flowglad(customerExternalId).getBilling()

  return {
    customer: billing.customer,
    activeSubscriptions: billing.subscriptions.filter(
      (s) => s.status === 'active'
    ),
    paymentMethods: billing.paymentMethods,
    recentInvoices: billing.invoices.slice(0, 10),
    features: billing.features,
  }
}

Integration Examples

Basic Setup

import { FlowgladServer } from '@flowglad/server'

export const flowglad = (customerExternalId: string) => {
  // customerExternalId is the ID from YOUR app's database, NOT Flowglad's customer ID
  return new FlowgladServer({
    customerExternalId,
    getCustomerDetails: async (externalId) => {
      // Fetch customer details from YOUR database using YOUR app's ID
      const user = await db.users.findOne({ id: externalId })
      if (!user) {
        throw new Error('Customer not found')
      }
      return {
        email: user.email,
        name: user.name,
      }
    },
  })
}

// Usage:
// Pass YOUR app's user/organization ID, not Flowglad's customer ID
const billing = await flowglad(userId).getBilling()

Next Steps

Next.js SDK

Use with Next.js applications

Overview

SDKs

Additional Resources

​Overview

​Installation

​Installation

​Quick Start

​1. Set Up Environment Variables

​2. Create a FlowgladServer Factory Function

​3. Mount Flowglad Route Handler

​4. Call Server Methods

​Key Features

​API Reference

​Constructor

​Options

​Customer Methods

​findOrCreateCustomer()

​Billing Methods

​getBilling()

​getPricingModel()

​Subscription Methods

​createSubscription

​cancelSubscription

​uncancelSubscription

​Checkout Methods

​createCheckoutSession

​createAddPaymentMethodCheckoutSession

​createActivateSubscriptionCheckoutSession

​Customer Updates

​updateCustomer

​Feature Access Methods

​checkFeatureAccess

​Usage Tracking Methods

​createUsageEvent

​Common Patterns

​Feature Gating Middleware

​Usage Metering

​Customer Portal Generation

​Integration Examples

​Basic Setup

​Next Steps

Next.js SDK

Overview

Installation

Installation

Quick Start

1. Set Up Environment Variables

2. Create a FlowgladServer Factory Function

3. Mount Flowglad Route Handler

4. Call Server Methods

Key Features

API Reference

Constructor

Options

Customer Methods

`findOrCreateCustomer()`

Billing Methods

`getBilling()`

`getPricingModel()`

Subscription Methods

`createSubscription`

`cancelSubscription`

`uncancelSubscription`

Checkout Methods

`createCheckoutSession`

`createAddPaymentMethodCheckoutSession`

`createActivateSubscriptionCheckoutSession`

Customer Updates

`updateCustomer`

Feature Access Methods

`checkFeatureAccess`

Usage Tracking Methods

`createUsageEvent`

Common Patterns

Feature Gating Middleware

Usage Metering

Customer Portal Generation

Integration Examples

Basic Setup

Next Steps