1. Key Features:
- User Profiles: Allow users to create, edit, and manage their profiles, including username, photo, bio, and investment interests.
- Twit Functionality: Users can post short messages ("twits") with stock tickers ($AAPL, $GOOGL, etc.) and other content like images, links, and GIFs.
- Real-time Feed: A live feed where users can view recent twits from people they follow or based on particular stocks or sectors of interest.

- Trending Stocks: Highlight stocks that are currently trending based on volume of mentions and sentiment analysis.

- Watchlist: Allow users to create and manage a list of stocks they're interested in tracking.

- Direct Messaging: Allow users to send private messages to each other.

- Sentiment Analysis: Implement sentiment analysis on twits to gauge overall market sentiment on particular stocks or sectors.

- Notifications: Users receive notifications for mentions, new followers, and other relevant interactions.
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2. Advanced Features (Optional):
- Stock Charts Integration: Allow for the embedding or linking of real-time stock charts.

- Polls: Users can create polls to get opinions on specific stocks or market events.

- Community Boards: Creation of boards or forums for specific stocks, sectors, or market strategies where users can have more detailed discussions.
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3. Technical Requirements:
- Backend: Choose a robust backend system (like Node.js, Django, etc.) to handle user data, twits, and notifications.

- Database: Relational databases (PostgreSQL, MySQL) or NoSQL databases (MongoDB) for storing user profiles, twits, and other data.

- Frontend: React, Angular, or Vue.js for a responsive web frontend.

- APIs: Integration with stock price and news APIs, sentiment analysis tools, etc.

- Security: Implement secure authentication and encryption to protect user data and ensure privacy.
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4. Testing and QA:
- Unit Testing: Testing of individual components and functions.

- Integration Testing: Testing of interactions between different parts of the application.

- User Acceptance Testing: Beta testing with a group of users to gather feedback and make final adjustments.
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5. Milestones and Timeline:
1. Project kickoff
2. Design and prototype completion
3. Development of MVP (Minimum Viable Product)
4. Beta testing
5. Launch
6. Post-launch updates and maintenance

This is a high-level scope, and the actual details and requirements would depend on your specific needs, goals, and resources.
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6. StockTwits API Integration:

- API Authentication: Implement OAuth or the relevant authentication mechanism required by StockTwits to establish a secure connection.

- Fetch Stock Data: Retrieve real-time and historical stock data, including price, volume, and other relevant metrics.

- Fetch User Twits: Access and display twits related to specific stocks, sectors, or from specific users.

- Post Twits: Allow your platform's users to post twits directly to StockTwits (if the API allows).

- Sentiment Analysis: Leverage the StockTwits API to fetch sentiment data on specific stocks. This might include bullish or bearish sentiments provided by StockTwits users.

- Rate Limiting and Quotas: Implement handling for API rate limits to ensure your platform doesn't exceed the number of requests allowed in a specific timeframe.

- Error Handling: Implement robust error handling for potential issues like API downtime, incorrect data, or other unexpected responses.

- Caching: Consider caching frequently accessed data to improve performance and reduce the load on the API. This could be done using tools like Redis.
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7. Maintenance and Monitoring:

- API Versioning: Ensure that you are always compatible with the latest version of the StockTwits API and handle any deprecated endpoints or features.

- Monitoring: Monitor API calls to identify any issues, failures, or unexpected behaviors. Tools like Grafana or Prometheus can help visualize API metrics.

- Alerts: Implement alerting mechanisms to notify the dev team of any API-related issues or if you're nearing your API rate limit.

8. Documentation and Training:

- Internal Documentation: Create comprehensive documentation detailing how the StockTwits API has been integrated, including all endpoints used, data flow diagrams, and any customizations.

- Training: Train the support and development team on how the API integration works, potential issues they might encounter, and troubleshooting steps.

9. Costs and Budgeting:

- API Costs: Some APIs may have costs associated with high usage or premium features. Ensure you factor these into your project budget.

- Infrastructure Costs: Factor in costs related to the increased infrastructure needed to handle the API data flow, caching, and storage.
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Remember, when working with external APIs, always review the terms of service and ensure you adhere to the platform's rules and guidelines. It's also a good idea to keep an eye on any changes to the API documentation or policies, as these can affect your platform's functionality.