SOLVLOGS
Real problems. Exact diagnosis. Step-by-step solutions. Written by engineers for engineers.
Duplicate Stripe Charges Were Causing Customer Complaints
Customers were being charged twice. The Stripe integration worked correctly. The problem was missing idempotency keys, no server-side duplicate detection, and a frontend that allowed multiple submissions. Here is the full investigation and the fixes that brought duplicate charges to zero.
Google OAuth Verification Kept Getting Rejected Until We Fixed These Issues
Our Google OAuth verification was rejected five times. The application worked perfectly every time. Here is what we actually got wrong and the systematic approach that finally got us approved.
Our Facebook and Instagram App Review Kept Failing Until We Fixed These Issues
Our Meta app review failed five times. The code worked perfectly every time. Here is what we actually got wrong and the systematic approach that finally got us approved.
Salesforce Integration Guide: Accounts, Leads, Opportunities, Sync, and Enterprise Automation
A complete Salesforce CRM integration guide covering accounts, leads, opportunities, Platform Events, Change Data Capture, OAuth 2.0, and enterprise automation across every major frontend and backend stack.
HubSpot CRM Integration Guide: Contacts, Deals, Workflows, Webhooks, and Automation
A complete HubSpot CRM integration guide covering contacts, deals, webhooks, OAuth 2.0, and workflow automation across every major frontend and backend stack.
AWS Bill Doubled Overnight: Complete Diagnosis Guide
You open the AWS billing console and the current month's bill is already double last month's total. Use Cost Explorer, AWS CLI queries, and service-specific checks to pinpoint the source within 30 minutes.
EC2 Costs Suddenly Increased Without Traffic Growth
Your EC2 bill grew 80% but application traffic is unchanged. Walk through instance audits, EBS volume cleanup, Reserved Instance expiry checks, and Savings Plans coverage gaps to find exactly what changed.
RDS Costs Increased Dramatically: Common Causes
Your RDS bill jumped 100-300% with no change in query volume. Trace the increase to Multi-AZ, storage autoscaling, backup retention policy changes, Aurora Serverless ACU scaling, Enhanced Monitoring, or accumulated manual snapshots.
Vercel Deployment Works Locally but Fails in Production
npm run build succeeds on your machine and in CI but Vercel either fails the build or the deployed app crashes immediately. Trace the root cause through environment variable gaps, Edge Runtime module restrictions, function size limits, and runtime version mismatches.
Docker Container Keeps Restarting in Production
Your container starts, crashes, and Docker immediately restarts it over and over. Systematically diagnose OOM kills, missing startup environment variables, health check misconfiguration, dependency race conditions, and PID 1 signal handling to stop the restart loop.
PostgreSQL Performance Degraded After Growth
PostgreSQL performance problems at scale follow a predictable pattern: missing indexes on filter columns, table bloat from deleted rows that autovacuum cannot keep up with, stale statistics causing the query planner to choose sequential scans, and connection pool exhaustion. Each is diagnosable with built-in tools.
Redis Memory Usage Keeps Growing Unexpectedly
Redis memory that grows without bound almost always traces to keys with no TTL, caching of objects that are too large, using Redis as a primary database without expiry policies, or a missing maxmemory-policy. Here is how to find the problem with redis-cli.
Stripe Connect Verification Failed for Marketplace Users
Users completing your marketplace onboarding hit a verification wall Stripe rejects their identity documents or the connected account silently enters a restricted state. Here is the exact diagnosis path we followed.
Stripe Subscription Status Not Updating After Payment
Customers pay successfully, Stripe shows the subscription as active, but your database still shows past_due or canceled. The webhook handler exists but it is not running the right logic for the right events.
Stripe Checkout Successful but Order Was Never Created
Payment succeeded, customer sees the success URL, but no order was created in your backend. This is one of the most costly bugs in an e-commerce integration here is exactly how it happens and how to fix it.
Payment Succeeded but User Access Was Never Activated
Payment goes through on Stripe's end, but the user's account tier never changes. This is almost always a webhook event type mismatch combined with no fallback synchronization. Here is the full diagnosis.
Stripe Processing Duplicate Webhook Events
Stripe guarantees at-least-once webhook delivery. That means duplicates are not a bug in Stripe they are a fact of life. Your webhook handler must be idempotent. Here is how to build that correctly.
Clerk Authentication Redirect Loop After Deployment
A Next.js app with Clerk auth works perfectly in development but enters an infinite redirect loop in production. The root cause is almost always middleware misconfiguration publicRoutes not declared, afterSignInUrl pointing back to a protected route, or a missing environment variable in the deployment.
Google OAuth Verification Keeps Getting Rejected
Google's OAuth app review process rejects applications for reasons that are rarely obvious from the rejection email. This post documents the exact requirements for sensitive and restricted scopes, what your privacy policy page must contain, and how to configure the OAuth consent screen to pass review.
Facebook App Review Rejected: Common Reasons and Fixes
Meta's app review process rejects applications with error messages that rarely indicate what actually needs to change. This post documents the real reasons apps get rejected, what the review team looks for in screencasts, and the exact configuration changes that lead to approval.
Instagram App Review Keeps Failing? Here's What Meta Wants
Instagram Graph API permissions require App Review approval and the review criteria are specific to Instagram's platform policies. This post documents why instagram_basic, instagram_content_publish, and related permissions get rejected and the exact steps to get them approved.
Auth0 Callback URL Mismatch in Production
An Auth0 application that works perfectly in development starts throwing 'callback URL mismatch' errors after deploying to production. The fix is in the Auth0 dashboard Allowed Callback URLs list, but the details matter: HTTP vs HTTPS, trailing slashes, environment-specific configuration, and wildcard URL gotchas all contribute to the problem.
WhatsApp Business API Messages Not Delivering
Your API calls return 200 OK but recipients never see the messages. Walk through every layer number verification, template approval, session windows, quality ratings, opt-outs, and rate limits to find exactly which gate is closed.
WhatsApp Webhooks Not Reaching Your Server
Meta is sending webhook events but your server never processes inbound messages or delivery receipts. Trace the failure through token verification, SSL validation, response codes, body parsing, and subscription field configuration.
WhatsApp Quality Rating Dropped Suddenly
Your number's quality rating dropped to YELLOW or RED and your messaging tier was downgraded. Learn what triggers the drop, how Meta calculates quality, and the exact steps to recover without losing your phone number.
OpenAI API Rate Limits Breaking Your Application
Your application is throwing 429 RateLimitError at random intervals, bringing down request pipelines and frustrating users. Here is the systematic fix.
Why Your OpenAI API Bill Increased Overnight
Your OpenAI spend doubled without a traffic increase. The culprit is almost always prompt bloat, missing caching, or the wrong model for the job.
OpenAI Responses Became Slow in Production
OpenAI completions that took 2 seconds now take 15 seconds. The fix starts with streaming and ends with model selection and parallel request design.
RAG System Returning Incorrect AI Responses
Your RAG system confidently returns wrong answers. The bugs are in your chunking strategy, similarity threshold, or context assembly not the LLM.
AI Agent Tool Calls Randomly Failing in Production
Your AI agent calls the wrong tools, generates malformed JSON, or silently drops tool results. The bug is in your schema definition or response handling.
The Complete SaaS Technology Stack for 2026
Choosing the wrong technology stack can slow development, increase costs, and create scaling problems that are painful and expensive to fix. This guide covers every layer of a modern SaaS stack with concrete recommendations for each growth stage.
Users Sign Up but Never Become Paying Customers
High signup volume and low paid conversion is one of the most demoralising SaaS metrics to stare at. It tells you acquisition is working but something between sign-up and payment is broken. Here is how to find it.
Launched Your MVP but Users Aren't Returning?
Launching an MVP and watching DAU flatline after the initial surge is a specific kind of product failure. It usually means core value delivery is too slow, the habit loop is missing, or the wrong users showed up. Here is how to diagnose it.
SaaS Churn Increased Suddenly: What to Check First
A sudden churn spike is different from gradual churn growth it points to a discrete event. Knowing which event to look for first is the difference between recovering in two weeks or spending three months on the wrong diagnosis.
Customer Support Requests Grew Faster Than Your Team
When support ticket volume grows faster than headcount, the instinct is to hire. The better instinct is to ask why tickets are being generated at all. Most support overload is a product problem with a UX fix, not a staffing problem with a hiring fix.
Your Application Was Fast at 100 Users. Why Is It Slow at 10,000?
Performance that was fine at small scale almost always degrades through the same patterns at growth: N+1 queries, missing indexes, no caching, synchronous blocking, and missing pagination. The good news is these are all diagnosable and fixable without a rewrite.
Clerk Authentication Integration Guide: Secure Auth for Modern SaaS Applications
Building authentication from scratch is expensive and risky. Clerk gives SaaS products enterprise-grade auth, social logins, organizations, and RBAC in days. This guide covers the full integration across every major frontend and backend stack.
Slack API Integration Guide: Automating Notifications, Workflows, and Internal Operations
Missed alerts, manual workflows, and slow team communication cost engineering teams hours every week. This complete Slack API integration guide covers webhooks, bots, slash commands, Events API, and automation examples across every major backend and frontend stack.
Prisma + Vercel: Fixing Connection Pool Exhaustion (P1001 / P1017 Errors)
A Next.js app on Vercel starts throwing P1001 or P1017 errors in production under load. The fix is not what most developers reach for first, here is the correct diagnosis and the exact steps to resolve it.
How to Fix Nginx 502 Bad Gateway Error: Causes and Solutions
A 502 Bad Gateway means Nginx is running but the application behind it is not responding. This is the exact workflow we use to diagnose and fix it in under ten minutes.
OpenAI API Integration Guide: Architecture, Implementation, Security, and Automation
Everything you need to integrate the OpenAI API into a production application, from architecture decisions and frontend code to backend implementation, security, automation, and deployment.
WhatsApp Business API Integration Guide: Architecture, Automation, Security, and Implementation
Everything you need to integrate the WhatsApp Business API into a production system, from Meta App setup and webhook handling to AI automation, CRM sync, security, and a deployment checklist.
Stripe Payment Integration Guide: Architecture, Webhooks, Security, and Subscription Billing
Everything you need to integrate Stripe into a production application, from Checkout Sessions and Payment Intents to webhook handling, subscription lifecycle management, failed payment recovery, and PCI compliance.