Beginner LevelSystem Design & Architecture
Why is Idempotency critical in distributed payment and order processing systems?
❓ Interview Prompt: Explain Idempotency, handling network timeouts, duplicate request retries, Idempotency Keys, and atomic state updates.
In distributed systems, network requests can time out without the client knowing if the server processed the request. If the client retries the request, an un-idempotent system executes the action twice!
Idempotency Solution:
An operation is Idempotent if executing it multiple times yields the exact same result as executing it once.
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Implementation: Clients send a unique 'Idempotency-Key' header with payment requests ('POST /charge'). The server tracks processed keys in Redis, returning cached responses for duplicate retries.
Code Implementation Example
typescript
export async function processIdempotentCharge(idempotencyKey: string, amount: number) {
const existing = await redis.get('idempotency:\${idempotencyKey}');
if (existing) return JSON.parse(existing); // Return cached result for retries!
const result = await stripe.charges.create({ amount });
await redis.setex('idempotency:\${idempotencyKey}', 86400, JSON.stringify(result));
return result;
}💡Processing payment charges safely using Idempotency Keys.
🎯 Interview Key Takeaway
Enforce Idempotency Keys on all state-changing endpoints to protect against duplicate processing during client retries.
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