A Simple Security and Performance Checklist Before You Launch
You're close to shipping. The features work. The design looks good. But somewhere in the back of your mind there's a nagging worry: what if something breaks? What if there's a security hole you missed? What if the app is too slow and users bounce?
This checklist won't make your app bulletproof. Nothing will. But it covers the basics that prevent embarrassing problems on launch day. If you can answer yes to each section, you're ready to ship.
Perfection isn't required. Recoverability is.
Web Apps
1. Are users and data protected at a basic level?
This is table stakes. Private pages should actually require login. Users should not be able to see or edit other users' data. Admin actions should be locked down and inaccessible to regular users.
The most common mistake is assuming the frontend handles authorization. It doesn't. If your API endpoints don't verify that the requesting user has permission to access the requested resource, someone will eventually discover they can modify the URL or API call and access things they shouldn't.
Prompt to try:
"Act like a security reviewer. Given this app description and routes: [paste], list any obvious ways users could see or modify data they shouldn't."
2. Are secrets actually secret?
API keys should never appear in frontend code. Environment variables need to be set correctly in production. Test keys and development credentials should not be anywhere near your production environment.
This sounds obvious, but it happens constantly. Someone commits a .env file. Someone hardcodes a key "just for testing" and forgets to remove it. Someone pushes to production and wonders why payments are going to a test account.
Prompt to try:
"Scan this code/config for exposed secrets or unsafe environment variables: [paste]."
3. Is basic abuse prevented?
Login and signup endpoints should have rate limiting. Forms need basic validation. File uploads, if you have them, should have size limits and type restrictions.
If someone can hammer your signup endpoint a thousand times per second, they will. If someone can upload a 2GB file to your profile picture endpoint, they might. Assume users will do weird things, both malicious and accidental, and put guardrails in place.
Prompt to try:
"Given these endpoints and forms: [paste], where could this app be abused or spammed easily?"
4. Does the app feel fast enough?
First page loads should be quick. Buttons should respond immediately. Images should not block the page from becoming interactive.
Perceived performance matters more than benchmark numbers. Users don't care about your Lighthouse score; they care whether the app feels snappy. If the main content appears quickly and interactions respond instantly, minor background loading is fine.
Prompt to try:
"Given this app and a Lighthouse report: [paste], what are the top 5 changes that would most improve perceived speed?"
5. Will you know if something breaks?
Errors need to surface somewhere. Sentry, LogRocket, server logs, something. You need to be able to tell if users are failing to log in, hitting errors, or dropping off at specific steps.
Shipping without error tracking is flying blind. The first you'll hear about problems is angry emails or one-star reviews, and by then you've already lost users. Set up basic monitoring before you launch.
Prompt to try:
"What is the minimum error tracking and logging I should add before launch for this app?"
6. Can you recover if something goes wrong?
You should know how to turn the app off or roll back to a previous version. Data should be backed up in some form.
The question isn't whether something will go wrong. It's when. A bad deploy, a database issue, a third-party service outage. If you can roll back quickly, a bad situation becomes a minor incident. If you can't, it becomes a crisis.
Prompt to try:
"Given this stack: [paste], what is the simplest rollback and backup plan I can use at launch?"
Mobile Apps
Mobile apps have some unique considerations. The checklist is similar in spirit but different in specifics.
1. Are accounts and sessions safe?
Login tokens should be stored securely, not in plain text or AsyncStorage without encryption. Logging out should actually clear the session. Sensitive screens shouldn't be accessible if the user isn't authenticated.
Mobile security also means thinking about the device itself. What happens if someone steals the phone? Can they access sensitive data? Biometric authentication for sensitive actions can help.
Prompt to try:
"Review this mobile auth flow and token storage: [paste]. What are the biggest launch-blocking risks?"
2. Is user data treated carefully?
Only store sensitive data if you actually need it. Don't log private information to the console or crash reports. Make sure analytics events don't accidentally include PII like email addresses or phone numbers.
This is both a privacy issue and a compliance issue. Depending on your users and markets, regulations like GDPR may apply. Even if they don't, treating user data carefully builds trust.
Prompt to try:
"Given this analytics and logging setup: [paste], what private data might leak?"
3. Does the app feel responsive?
The app should open quickly. Scrolling should be smooth. Images and lists shouldn't stutter or freeze.
Mobile users have high expectations for responsiveness. A web app that takes a second to load might be forgiven; a mobile app that stutters while scrolling will get deleted. Test on real devices, not just simulators.
Prompt to try:
"Given this screen and list implementation: [paste], what are the top 3 performance fixes?"
4. Will crashes be visible?
Crash reporting should be enabled before you ship. You should be able to see crashes broken down by version, device type, and OS version.
Tools like Sentry, Bugsnag, or Firebase Crashlytics make this straightforward. There's no excuse for shipping without crash visibility. You need to know when things break so you can fix them.
Prompt to try:
"What is the minimum crash reporting setup I should add before shipping this app?"
5. Will app store reviewers reject it?
Permission requests should match actual features in your app. A privacy policy needs to exist. Marketing copy shouldn't make claims your app can't back up.
App store rejections are frustrating because they delay your launch and the feedback is often vague. Review Apple's and Google's guidelines before you submit. Make sure your permission usage is justified and your metadata is accurate.
Prompt to try:
"Given this app description and permission list: [paste], what app store issues could block approval?"
The Final Gut Check
For web apps, if you can say:
The app loads fast. Users can't access each other's data. Errors surface somewhere. You can roll back if needed.
You're ready to ship.
For mobile apps, if you can say:
The app feels responsive. Users' privacy is protected. Crashes are visible. App store guidelines are followed.
You're ready to ship.
The Mindset
Launch day anxiety is normal. You will find bugs after you ship. Users will do things you didn't anticipate. Something will break.
The goal isn't to prevent all problems. It's to make sure you'll know about problems when they happen and can fix them quickly. A bug that's caught and fixed in an hour is a minor issue. A bug that goes unnoticed for a week is a disaster.
Set up your observability. Have your rollback plan ready. Then ship.
If you're building with Nucleate, this process is streamlined. You get a full development environment with Expo, can preview on real devices, and iterate quickly. When you're ready to launch, the basics are in place. But the security review, the performance testing, the final gut check? That's still on you. Tools help. Judgment ships.