💾 Historical Data Cache

🎯 What it does

TradePro stores historical OHLCV price data in your browser's IndexedDB database. The first time you run the Strategy Scanner or Pattern Recognition on a set of tickers, it fetches up to 5 years of daily data from Yahoo Finance via the Cloudflare Worker. That data is saved locally — the next scan loads directly from cache, skipping the API call entirely.

⚙️ How it works

1. Cache check

Before every API call, historical-data-service.js checks whether valid cached data already exists for the ticker and date range. "Valid" means the cache covers the requested range minus a 1-day tolerance (to handle weekends and holidays).

2. Delta fetch

If the cache exists but is missing recent days, only the missing period is fetched. For example, if cache covers up to last Friday and today is Tuesday, only Mon–Tue is fetched and merged.

3. Full refresh

Once a month (configurable), the full dataset for a ticker is re-fetched to pick up split-adjusted prices. Yahoo Finance already adjusts for splits via adjclose, but a monthly refresh ensures the entire series stays accurate.

4. Progress feedback

The strategy scanner progress bar shows live cache stats: how many tickers were served from cache vs. freshly fetched. Events cache-hit and cache-write are dispatched on window for real-time UI updates.

📦 Storage details

🛠️ Cache Settings

In the main app (index.html), open ⚙️ Settings → API Configuration and scroll to the "💾 Historical Data Cache" section. From there you can:

• View cache stats — total tickers cached, total rows, estimated size
• Clear all cache — wipes the entire IndexedDB database. The next scan rebuilds from scratch.
• Clear a single ticker — remove cache for one symbol only (useful after a known data issue)

❓ FAQ

Why does my first scan still take a long time?

The first scan always fetches all data fresh — there is nothing in cache yet. Subsequent scans benefit from the cache. Consider running a full scan overnight to warm the cache.

Data looks stale — what do I do?

Open Settings → Historical Data Cache and click Clear All Cache. The next scan will fetch everything fresh. This is also done automatically once a month per ticker.

The VWAP card is missing the last few days

This was a known bug (fixed in commit bf31d07). The cache now uses a 1-day tolerance and reads up to today's date. If you still see stale data, clear the cache for the affected ticker.

Does the cache work across different pages?

Yes — Strategy Scanner, Market Pattern Recognition, and Universal Market Scanner all share the same IndexedDB database. Data fetched on one page is available on all others.

Will clearing browser cookies/history affect the cache?

Cookies and history are separate from IndexedDB. However, clearing "all site data" or using browser privacy tools that wipe storage will remove the cache.