To efficiently store and manage frequently fetched data such as open orders, trade history, holdings, reports, and favorite symbols for each user in a scalable and high-performance manner, you can follow these best practices:

1. Database Schema Design

Design your database schema to optimize for read performance while ensuring data integrity. Here’s a suggested schema for the tables you mentioned:

Users Table

CREATE TABLE users (
    id SERIAL PRIMARY KEY,
    username VARCHAR(50) UNIQUE NOT NULL,
    password_hash VARCHAR(255) NOT NULL,
    email VARCHAR(100) UNIQUE NOT NULL,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

Open Orders Table

CREATE TABLE open_orders (
    id SERIAL PRIMARY KEY,
    user_id INT REFERENCES users(id),
    symbol VARCHAR(10) NOT NULL,
    order_type VARCHAR(10) NOT NULL, -- 'limit' or 'market'
    quantity INT NOT NULL,
    price DECIMAL(10, 2),
    status VARCHAR(20) DEFAULT 'open',
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
);

Trade History Table

CREATE TABLE trade_history (
    id SERIAL PRIMARY KEY,
    user_id INT REFERENCES users(id),
    symbol VARCHAR(10) NOT NULL,
    trade_type VARCHAR(10) NOT NULL, -- 'buy' or 'sell'
    quantity INT NOT NULL,
    price DECIMAL(10, 2) NOT NULL,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

Holdings Table

CREATE TABLE holdings (
    id SERIAL PRIMARY KEY,
    user_id INT REFERENCES users(id),
    symbol VARCHAR(10) NOT NULL,
    quantity INT NOT NULL,
    average_price DECIMAL(10, 2) NOT NULL,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
);

Favorite Symbols Table

CREATE TABLE favorite_symbols (
    id SERIAL PRIMARY KEY,
    user_id INT REFERENCES users(id),
    symbol VARCHAR(10) NOT NULL,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

2. Indexing

To improve query performance, especially for frequent fetches, create indexes on columns that are often queried:

CREATE INDEX idx_user_id ON open_orders(user_id);
CREATE INDEX idx_user_id ON trade_history(user_id);
CREATE INDEX idx_user_id ON holdings(user_id);
CREATE INDEX idx_user_id ON favorite_symbols(user_id);

3. Caching

Implement caching to reduce the load on your database and speed up data retrieval:

• In-Memory Caching: Use a caching layer like Redis or Memcached to store frequently accessed data. For example, you can cache the results of open orders, holdings, and favorite symbols for each user.
• Cache Expiration: Set appropriate expiration times for cached data to ensure that users see up-to-date information.