Beginner LevelSystem Design & Architecture
What is Stateless vs Stateful Service Architecture?
❓ Interview Prompt: Compare Stateless (no local session state) vs Stateful (local in-memory state) architectures, auto-scaling, and session storage.
Designing scalable web application tiers:
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Stateless Architecture: Application servers store zero client session state in local memory. Any request can be processed by any server instance. Session state is offloaded to a shared distributed cache (Redis) or JWTs. Enables instant auto-scaling!
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Stateful Architecture: Servers maintain client session state in local RAM. Requires sticky sessions on load balancers, complicating failover and horizontal auto-scaling.
Code Implementation Example
typescript
// Stateless Express Route: Offloading session state to Redis
app.get('/api/v1/profile', async (req, res) => {
const token = req.headers.authorization?.split(' ')[1];
const session = await redis.get('session:\${token}'); // Distributed session store!
if (!session) return res.status(401).send('Unauthorized');
res.json(JSON.parse(session));
});💡Stateless service reading session state from a distributed Redis cache.
🎯 Interview Key Takeaway
Architect application web tiers to be 100% stateless, storing user session state in distributed caches like Redis.
#System Design#Stateless#Stateful#Architecture#Beginner
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