Marketplace Plugin Development for SaaS – OAuth, Integrations, Plugins

You've launched a SaaS, and 80% of clients request integrations with CRM, accounting, telephony. Manual development of each integration takes 2–3 weeks, and support takes even more. The solution: a marketplace of plugins. We specialize in developing marketplace plugins and integrations for SaaS, including OAuth authorization and extension registry. A community of developers creates extensions, and users install them with a few clicks. The result is an ecosystem like Atlassian, Shopify, or Figma, built in 8–14 business days. We'll evaluate your project in one day and offer a turnkey solution.

Problems That a Marketplace Solves

Without a marketplace, each integration request is manual work. Developers spend hours on API negotiation, OAuth dances, and testing. Clients wait for weeks. Additionally, backend load increases—N+1 queries, suboptimal calls cause LCP to drop by 30%. A properly designed marketplace solves all this with a unified plugin registry, authorization templates, and ratings. For example, one client after launching a marketplace increased the number of integrations from 5 to 50 in six months—saving about $50,000 in development costs.

Architecture: Two Types of Extensions

Server-side integrations—OAuth applications that interact with your API on behalf of the user. A third-party service (e.g., Zapier or n8n) authorizes and calls your API.

Client-side plugins—JavaScript code executed in an iframe or Web Worker on the client side. The Figma Plugin Model is an example.

Plugin Registry

model Plugin { id String @id @default(cuid()) slug String @unique name String description String @db.Text author String authorUrl String? iconUrl String? category PluginCategory installCount Int @default(0) rating Float? isVerified Boolean @default(false) isPublished Boolean @default(false) // For server-side: OAuth credentials clientId String? @unique clientSecret String? // encrypted // Manifest permissions String[] // ['read:projects', 'write:tasks'] webhookUrl String? oauthConfig Json? installations PluginInstallation[] reviews PluginReview[] } model PluginInstallation { id String @id @default(cuid()) pluginId String tenantId String installedAt DateTime @default(now()) config Json? // settings for a specific installation accessToken String? // OAuth token of the tenant for the plugin plugin Plugin @relation(fields: [pluginId], references: [id]) tenant Tenant @relation(fields: [tenantId], references: [id]) @@unique([pluginId, tenantId]) } 

How Does the OAuth Flow Work During Plugin Installation?

The installation process for a server-side plugin is a typical OAuth 2.0 Authorization Code Grant. We generate a state for CSRF protection, redirect the user to the plugin's OAuth server, get a code, and exchange it for an access token. The token is encrypted and stored in the PluginInstallation model. After that, the plugin can call your API on behalf of the installing tenant. The implementation is based on the OAuth 2.0 specification.

// OAuth flow for installing a server-side plugin export async function initiatePluginInstall( tenantId: string, pluginSlug: string ): Promise<string> { const plugin = await db.plugin.findUniqueOrThrow({ where: { slug: pluginSlug } }); // Generate state for CSRF protection const state = await generateState({ tenantId, pluginId: plugin.id, action: 'install', }); // Redirect to the plugin's OAuth provider const authUrl = new URL(plugin.oauthConfig?.authorizationUrl as string); authUrl.searchParams.set('client_id', plugin.clientId!); authUrl.searchParams.set('redirect_uri', `${process.env.APP_URL}/marketplace/callback`); authUrl.searchParams.set('scope', plugin.permissions.join(' ')); authUrl.searchParams.set('state', state); authUrl.searchParams.set('response_type', 'code'); return authUrl.toString(); } // Callback after OAuth authorization export async function completePluginInstall( code: string, state: string ): Promise<void> { const { tenantId, pluginId } = await verifyState(state); const plugin = await db.plugin.findUniqueOrThrow({ where: { id: pluginId } }); // Exchange code for token const tokenResponse = await fetch(plugin.oauthConfig?.tokenUrl as string, { method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify({ code, client_id: plugin.clientId, client_secret: decryptToken(plugin.clientSecret!), redirect_uri: `${process.env.APP_URL}/marketplace/callback`, grant_type: 'authorization_code', }), }); const tokens = await tokenResponse.json(); await db.pluginInstallation.upsert({ where: { pluginId_tenantId: { pluginId, tenantId } }, create: { pluginId, tenantId, accessToken: encryptToken(tokens.access_token), }, update: { accessToken: encryptToken(tokens.access_token), } }); // Notify the plugin about installation if (plugin.webhookUrl) { await fetch(plugin.webhookUrl, { method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify({ event: 'plugin.installed', tenantId, timestamp: new Date().toISOString(), }), }); } await db.plugin.update({ where: { id: pluginId }, data: { installCount: { increment: 1 } } }); } 

API for Plugin Developers

Developers interact with your SaaS via OAuth-authorized requests. We validate the token, check permissions, and return data.

// Plugins interact via OAuth-authorized requests to your API // app/api/v1/[...]/route.ts export async function validatePluginRequest(request: Request): Promise<{ plugin: Plugin; tenantId: string; }> { const authHeader = request.headers.get('Authorization'); if (!authHeader?.startsWith('Bearer ')) { throw new ApiError(401, 'Missing authorization'); } const token = authHeader.slice(7); // Verify the token const installation = await db.pluginInstallation.findFirst({ where: { // In reality: verify JWT or search by token hash accessToken: encryptToken(token), }, include: { plugin: true } }); if (!installation) { throw new ApiError(401, 'Invalid token'); } return { plugin: installation.plugin, tenantId: installation.tenantId, }; } 

Marketplace UI

A catalog of plugins with search, category filtering, and an indicator of installed extensions. We render on the server (SSR) for fast LCP, and cache the state via Redis.

// app/marketplace/page.tsx export default async function MarketplacePage({ searchParams }: { searchParams: { category?: string; q?: string } }) { const plugins = await db.plugin.findMany({ where: { isPublished: true, ...(searchParams.category ? { category: searchParams.category as PluginCategory } : {}), ...(searchParams.q ? { OR: [ { name: { contains: searchParams.q, mode: 'insensitive' } }, { description: { contains: searchParams.q, mode: 'insensitive' } }, ] } : {}), }, orderBy: { installCount: 'desc' }, }); const tenant = await getCurrentTenant(); const installedPluginIds = new Set( (await db.pluginInstallation.findMany({ where: { tenantId: tenant!.id }, select: { pluginId: true }, })).map(i => i.pluginId) ); return ( <div> <MarketplaceSearch /> <CategoryFilter /> <PluginGrid plugins={plugins} installedIds={installedPluginIds} /> </div> ); } 

What's Included in Marketplace Development

• API documentation for developers (Swagger/OpenAPI) and Postman collection
• TypeScript SDK for quick integration
• Plugin moderation and verification system
• Load testing up to 1,000 installations per hour
• CI/CD pipeline (GitHub Actions + Docker)
• Training your team on marketplace operations
• 6 months of free support on the code

Each plugin undergoes manual review before publication: we analyze the code for vulnerabilities and verify compliance with declared permissions. OAuth tokens are encrypted with AES-256, webhook notifications are signed with HMAC. We guarantee that no plugin gains access to data beyond its scope.

Why a Marketplace Is Better Than Manual Integrations

Without a marketplace, you spend resources on every integration manually—three times slower than with a developer community. With a marketplace you get: a 40% quarterly increase in the number of integrations, reduced support load (users install plugins themselves), and additional revenue from a 10–30% commission. A marketplace is three times faster and five times cheaper when scaling compared to manual development. One client after launching a marketplace increased integrations from 5 to 50 in six months—saving about $50,000 in development costs. Additionally, monthly support savings reach $10,000.

Comparison of Plugin Types

Comparison of Approaches: Manual Integration vs Marketplace

What Are the Stages of Marketplace Development?

1. Analysis and audit of the current API—examine your endpoints, data model, determine if modifications are needed.
2. Design of the plugin registry—database schema, OAuth flow, permissions.
3. Backend implementation—registry, OAuth, webhook, developer API.
4. UI catalog development—store page, plugin card, installation workflow.
5. Developer documentation—SDK examples, Postman collection.
6. Testing—load testing (up to 1,000 installations per hour), security (pentest).
7. Deployment to chosen hosting—Vercel, AWS, Selectel—with CI/CD.

Our Experience

We have 5+ years building SaaS ecosystems. During this time, we've delivered 12 marketplace projects for products of various scales—from startups to enterprise with 10,000+ users. Our engineers hold AWS and Kubernetes certifications. We guarantee: secure token storage, performance up to 500 rps per instance, transparent documentation. Contact us to get a consultation and project estimate within one business day. Order an audit of your API—we'll determine integration complexity and exact timelines.