Codify SaaS Blog - Page 9
Code-first guides and deep dives on building B2B SaaS products, designing APIs, scaling web apps, and modernizing legacy software.
How to Build a SaaS Onboarding Flow That Actually Converts New Users
Most SaaS onboarding flows are technically broken — they lose state on refresh, have no resume logic, and track nothing. Here is the full implementation with URL-based steps, localStorage persistence, conditional branching, and analytics.
File Upload Architecture for SaaS — Direct S3 Upload With Presigned URLs in NestJS
Most SaaS apps funnel file uploads through their application server — paying the bandwidth cost twice and blocking request threads while files transfer. Here is the presigned URL approach with NestJS, frontend upload, validation, virus scanning, and image processing.
How to Build a SaaS Billing Portal — Stripe Customer Portal vs Custom Implementation
Stripe Customer Portal works out of the box and covers most billing needs. But it has branding limits and rigid flows. Here is how to decide between hosted portal and custom UI — with implementation code for both.
Next.js Internationalization for SaaS — How We Support Multiple Languages and Currencies
Adding i18n to a Next.js SaaS is more than translating strings — you need locale routing, RTL layout support, currency formatting with proper separators, pluralization rules, and a translation workflow that scales. Here is the full implementation with next-intl.
SaaS Dashboard Architecture in Next.js — How We Structure Complex Admin Interfaces
Most SaaS dashboards start simple and become unmaintainable. Here is the layout hierarchy, data fetching strategy, state management, and component architecture we use to keep them clean.
How to Integrate Third-Party APIs Reliably — Patterns We Use to Handle Failures
Third-party API integrations fail at the worst possible time. Here are 7 reliability patterns we use in production — timeout, retry, circuit breaker, fallback, abstraction, monitoring, and testing — with full NestJS code.
Stripe Subscription Billing in NestJS — Complete Implementation With Webhooks
A quarter of your SaaS churn is billing failures, not product problems. Here is a complete Stripe subscription billing implementation in NestJS with every critical webhook event handled — checkout, invoices, failed payments, plan changes, cancellations, and dunning.
How to Build a Public Developer API for Your SaaS — Documentation, SDKs and Sandbox
A public developer API is the difference between a SaaS that third-party developers can integrate with in hours versus weeks. Here is how we build them — OpenAPI docs, sandbox environments, auto-generated SDKs, developer portals, rate limiting tiers, and abuse handling.
REST API Design Mistakes We Made on Our First SaaS and How We Fixed Them
We made every REST API design mistake you can make building a SaaS. Verbs in URLs, no versioning, no pagination, no idempotency, no rate limiting — and we fixed them all. Here is exactly what we changed and why.
GraphQL vs REST for SaaS APIs — A Decision We Made for a Real Project
A client specifically requested GraphQL for their SaaS dashboard. Here is exactly how we evaluated GraphQL vs REST, what we chose, the nestjs/graphql implementation, DataLoader, auth resolvers, and the things GraphQL made harder.
API Versioning Strategies — How We Handle Breaking Changes Without Breaking Client Integrations
The breaking change that broke a client's integration at 2am taught us everything about API versioning. Here is how we handle URL and header versioning, deprecation timelines, NestJS versioned controllers, and database migrations across API versions.
Idempotency in SaaS APIs — How to Make Your Endpoints Safe to Retry
Idempotency is the difference between a network timeout that costs you a customer and one you never notice. Here is a complete API idempotency implementation for NestJS — idempotency keys, database deduplication, interceptors, race condition handling, and testing — so your endpoints are safe to retry.