How do you implement a custom session management system?

Question

Accepted Answer

**Session management** — track user state across requests.

```javascript
const crypto = require("crypto");

class SessionStore {
    constructor(options = {}) {
        this.sessions = new Map();
        this.ttl = options.ttl || 3600000; // 1 hour
        this.cleanupInterval = setInterval(() => this.cleanup(), 60000);
    }

create(data = {}) {
        const id = crypto.randomBytes(32).toString("hex");
        this.sessions.set(id, {
            data,
            createdAt: Date.now(),
            lastAccessed: Date.now(),
        });
        return id;
    }

get(id) {
        const session = this.sessions.get(id);
        if (!session) return null;

if (Date.now() - session.lastAccessed > this.ttl) {
            this.sessions.delete(id);
            return null;
        }

session.lastAccessed = Date.now();
        return session.data;
    }

set(id, data) {
        const session = this.sessions.get(id);
        if (session) {
            session.data = { ...session.data, ...data };
            session.lastAccessed = Date.now();
        }
    }

destroy(id) {
        this.sessions.delete(id);
    }

cleanup() {
        const now = Date.now();
        this.sessions.forEach((session, id) => {
            if (now - session.lastAccessed > this.ttl) {
                this.sessions.delete(id);
            }
        });
    }
}

// Express middleware
const sessions = new SessionStore();

app.use((req, res, next) => {
    const sessionId = req.headers.cookie?.match(/sid=([^;]+)/)?.[1];
    req.session = sessions.get(sessionId);

if (!req.session) {
        const id = sessions.create();
        res.setHeader("Set-Cookie", `sid=${id}; HttpOnly; SameSite=Strict`);
        req.session = sessions.get(id);
    }

next();
});
```

Node.js: How do you implement a custom session management system?