From the Team
Engineering Blog — Guides & Tutorials
Architecture decisions, tech stack deep-dives, and lessons from building real products.
How to Connect Next.js with Supabase: Auth, Database & Real-Time (2026)
A comprehensive guide to integrating Supabase with Next.js or React — covering database queries, authentication, Row Level Security, and real-time subscriptions.
Fix: Invalid API Key Error in Supabase
Seeing 'Invalid API key' from Supabase? Here's exactly why it happens and how to get your keys and env vars right.
Fix: JWT Expired Error in Supabase Auth
Getting a 'JWT expired' error from Supabase Auth? Here's why sessions expire and how to make refresh actually work.
Fix: relation does not exist in Supabase
Supabase or Postgres saying a table's relation does not exist? Here's how to find the real cause and fix it fast.
Fix: Supabase 'Failed to fetch' Error
Seeing 'Failed to fetch' when your app calls Supabase? Here's how to diagnose the real cause and fix it fast.
Fix: Supabase Session Missing After Page Refresh
Users getting logged out every time they refresh the page? Here's why Supabase session state disappears and how to fix it in Next.js.
Fix: Supabase 'Email Rate Limit Exceeded'
Signups or password resets failing with 'email rate limit exceeded'? Here's why Supabase's default email service is capped and how to fix it.
Fix: Firestore 'Missing or Insufficient Permissions'
Getting Missing or insufficient permissions in Firestore? Here's exactly why it happens and how to fix your security rules.
Fix: Firestore 'The Query Requires an Index'
Firestore says the query requires an index? Learn why composite queries need one and how to create it in minutes.
![Fix: Firebase '[DEFAULT] Already Exists' Error](/_next/image?url=%2Fimages%2Fblog%2Ffix-firebase-default-app-already-exists%2Fhero.webp&w=3840&q=75)
Fix: Firebase '[DEFAULT] Already Exists' Error
Seeing Firebase App named DEFAULT already exists? Here's the exact guard clause that stops it for good.
Fix: Firebase auth/invalid-api-key Error
Seeing auth/invalid-api-key in Firebase? Here's why it happens and the exact fix.
Fix: Next.js Image 'hostname not configured' Error
Getting hostname is not configured under images in next.config.js? Here's the fix.
Fix: Vercel 404 NOT_FOUND After Deploy
Deployed to Vercel and getting 404: NOT_FOUND? Here's why, and how to fix it.
Fix: "new row violates row-level security policy" in Supabase
The Supabase "new row violates row-level security policy" error means RLS blocked your insert. Here's exactly why it happens and how to fix it, with SQL examples.
How to Fix CORS Errors in Supabase Edge Functions (2026)
Getting a CORS error calling a Supabase Edge Function from the browser? Here's why it happens and the exact code to handle the preflight request and fix it.
Fix: Vercel Build Fails After Adding Supabase Env Variables
Your app builds locally but Vercel fails after adding Supabase? It's almost always environment variables. Here's how to fix it in a few minutes.
Fix: Lovable White Screen or Build Failed After Publish
Published a Lovable app and got a blank white screen or build error? Here's how to find the real cause in 30 seconds and the most common fixes.
Bolt.new Review 2026: Can It Really Ship Production-Ready Apps?
An honest, developer-led Bolt.new review — how StackBlitz's AI app builder works, its pricing and token model, what it nails, and where you still need a real developer.
How to Download a ZIP File From Replit (3 Methods, 2026 Guide)
Step-by-step guide to downloading your project as a ZIP file from Replit — covering the UI method, Git method, and how to handle common errors.
How to Connect a GoDaddy Domain to Vercel (2026 Step-by-Step Guide)
Step-by-step guide to pointing your GoDaddy domain to a Vercel deployment — including DNS records, SSL, and fixing propagation issues.
How to Set Up Cloudflare DNS: Complete Step-by-Step Guide (2026)
Learn how to set up Cloudflare DNS — from adding your site and updating nameservers, to configuring SSL, security, and performance settings.
How to Export Code From Lovable to GitHub or Local (2026 Guide)
Learn how to export your Lovable project to GitHub or run it locally — so you can self-host, extend, or hand off to a developer.
How to Set Up Resend Transactional Email in Next.js (2026 Guide)
Complete guide to setting up Resend — from domain verification and DNS records to sending your first email with Next.js and React Email templates.
How to Connect GitHub With Lovable (2026 Step-by-Step Guide)
Sync your Lovable project to GitHub in a few clicks — set up two-way sync, work locally, and keep real version control. A clear step-by-step guide.
How to Connect a Custom Domain to Lovable (2026 Step-by-Step Guide)
Point your custom domain to a Lovable project — publish, connect the domain, set the DNS records, and enable HTTPS. A clear step-by-step walkthrough.
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