Case study · P/03 Live on the App Store

Aura

A private mood journal with an AI companion: check in with a tap, and get a gentle note back.

Download on the Aura: App Store

Role: Solo developer: design, mobile, backend and AI
Timeline: 2024 – present
Platforms: iOS
Status: Live on the App Store

Fig. 1 The "pencil notebook" design direction

Apr 2024

launched on the App Store
~1 month

from idea to App Store

§ 1 · Overview

The product

Aura is a daily mood journal. You check in by picking how you feel, optionally add a line and a few tags, and Aura, the cat who lives in the notebook, answers with a short, kind note. Over time it surfaces the small things that help you feel like yourself.

I took the first version from empty repository to the App Store in about a month (March–April 2024): an Expo app, a serverless AWS backend, and an LLM companion running on Amazon Bedrock. I'm now rebuilding it as "the pencil notebook": no streaks, no ads, no account, and pages that stay on your phone.

Key features

One-tap daily mood check-in, with optional notes and tags
An AI companion that answers each entry with a short note
A monthly mood calendar

§ 2 · Engineering

How it's built

01 App
- React Native (Expo)
02 Auth
- Cognito identity pool
- SigV4-signed calls
03 API
- API Gateway (IAM)
- Python Lambdas
- Reserved concurrency
04 AI & ops
- Claude 3 Haiku (Bedrock)
- CloudWatch alarm
- SNS → kill switch

Fig. 2 Launch architecture.

01

Serverless AI backend with cost protection

The app talks to a small AWS backend (API Gateway, Python Lambdas, Claude on Bedrock) without requiring an account: requests are signed with anonymous Cognito credentials. If usage spikes, a CloudWatch alarm alerts me and automatically throttles the AI function.
02

In progress: a privacy-first rebuild

The next version keeps journal entries on the phone, runs on a backend with no database that never logs what people write, and falls back to on-device behaviour when the AI is unavailable.