tl;dr: Stock tracker web app for tracking and screening stocks

• Add/remove stocks from watchlist
• Real-time(ish) prices + daily charts
• Stock search by company/ticker
• Interactive price charts
• Zero auth, instant, free access - stores everything locally
• Built for speed-to-market

• No rate limiting
• 2k-3k concurrent users before rate limit hits
• Unofficial Yahoo Finance API (lol)

Browser's localStorage for v1. Reasons:

• 0 backend complexity
• Allows us to ship instantly
• Good enough for first users to gauge demand Alternatively, I would add a simple backend with a Postgres database (supabase) to store the watchlist.

No auth for v1. Instead:

• Use localStorage for watchlists
• Add newsletter signup (Substack) to capture emails
• Defer auth until we have user demand
• Focus on core value first

To harvest user emails:

• Use newsletter signup (Substack)
• Add something like posthog to track more fine-grained events related to users
• Idea: Provide a simple, valuable service like personalized, automated email-based daily newsletter based on the user's watchlist, using Google RSS feeds and a lightweight model (Haiku or 4o mini) to summarize the news

Simple 60-second polling because:

• Meets "1 min delay acceptable" requirement
• Much simpler than WebSockets
• Easy to implement
• Low server load
• Good enough for v1

Can add simple rate-limiting middleware to this, via Upstash Redis, or manually implement it for in-session requests and Yahoo Finance API, honestly.

3 clean endpoints:

1. Search for stocks GET /api/search?q= => [{symbol, name, exchange}]

2. Get current prices GET /api/stocks?symbols=AAPL,MSFT => [{symbol, price, change, changePercent}]

3. Get historical prices for charts GET /api/stocks/history?symbol=AAPL&range=1d => [{time, price}]

If we add auth, we would add OAUTH 2.0 via Google using a provider-agnostic library like Clerk or Supabase Auth so we can add more providers later.

For fastest v1:

• Next.js
• React
• Tailwind/shadcn
• Yahoo Finance API
• TypeScript
• Vercel