WriteBetter
WriteBetter is an AI-powered custom keyboard for Android and iOS that helps anyone write clearer, more confident messages without leaving the app they're in. Choose a tone, rewrite a sentence, translate, or fire off a smart reply, all from a keyboard built natively in Kotlin and Swift.
- Industry
- AI · Productivity · Mobile
- Discipline
- AI Productivity
Technologies used
Product overview
WriteBetter replaces the system keyboard with a smart one. While typing in any app, chats, email, social, users can rewrite their text, switch tone, translate, generate captions, or pull a smart reply, then drop the result straight into the conversation. It ships as a native Android app (Kotlin + Jetpack Compose) and a native iOS app (Swift), each with a companion app for settings, themes and subscription.
The challenge
A keyboard is one of the most demanding things to build well: it has to feel instant, work inside every other app, respect privacy, and still layer in AI without getting in the way. We needed AI rewriting and smart replies to feel like a natural part of typing, not a separate tool users have to switch to.
A real custom keyboard, not a wrapper
On Android the keyboard is a true input method (IME) service that manages the full typing experience, letters, numbers and symbols, shift and caps, key previews, long-press and delete-repeat, with AI, Paste Mode, Smart Replies, Translate and Clipboard available as in-keyboard panels. The iOS version delivers the same experience natively in Swift, so it feels at home on each platform.
AI that lives in the keyboard
Tones and rewrites let users instantly turn a rough sentence into something professional, casual, witty or persuasive. Smart replies suggest context-aware responses, translation switches languages on the fly, and voice typing turns speech into clean text, all without copying text out to another app.
Personalization & polish
Users can tailor the keyboard with themes, font styles, an extra number row, an expanded space bar, haptics and height settings, all shared between the keyboard and the companion app through saved preferences. A built-in onboarding tour and tooltips help new users discover the AI features quickly.
Built to ship & scale
WriteBetter is wired with Firebase for analytics and crash reporting and an in-app subscription system for premium tones and features. It's live on both the App Store and Google Play under Webnyxa Technologies, with a steady cadence of updates across both platforms.
A backend that protects the bill
Behind the keyboard sits a NestJS API running serverless on AWS Lambda. Out of the box, every request — legitimate or abusive — invoked Lambda and added to the bill. We re-architected the edge into three layers: CloudFront caches public config responses so repeated identical requests are served from the edge and never reach the origin; AWS WAF rate-limits abusive IPs and blocks common attacks (SQLi, XSS, bad bots) before the gateway; and API Gateway throttling adds a free hard ceiling on burst traffic. A forwarded origin secret stops anyone bypassing CloudFront by calling the raw gateway URL directly. The result: cached config routes dropped from roughly 10,000 Lambda invocations per hour to a handful, with cost and abuse both controlled at the edge.
Key features
Outcomes
- Live on both the App Store and Google Play.
- AI writing help available without leaving the current app.
- One consistent experience delivered natively on Android and iOS.
- Frequent shipping cadence across both platforms.
- Cut Lambda invocations on cached config routes from ~10,000/hour to single digits with CloudFront edge caching.
- Per-IP WAF rate limiting and AWS managed rules block abuse and common attacks before they reach — and bill — the backend.
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