Public Solution
Social Feed 1 - MVP Launch
Social Feed 1 - MVP Launch solution gives a production-minded baseline for this prompt. You get a concise requirements recap, a component-by-component architecture breakdown, explicit tradeoffs for latency, availability, cost, and complexity, plus failure mitigations and scoring rationale so you can benchmark your own design quickly.
Requirements Recap
| Requirement | Target |
|---|---|
| Registered users | 100,000 |
| Daily active users | ~20,000 |
| Avg posts per user/day | 3 |
| Avg follows per user | 50 |
| Post size | ≤ 300 characters |
| Timeline load time | < 500 ms |
Architecture Breakdown (Component-by-Component)
1. Web Clients
Generates user traffic and receives responses.
Acts as an entry layer that routes traffic into the rest of the system.
2. API Gateway
Handles api gateway responsibilities in this design.
Bridges 1 incoming flow to 1 downstream dependency.
3. API Service
Runs core business logic and orchestrates downstream calls.
Bridges 1 incoming flow to 3 downstream dependencies.
4. Redis Cache
Stores hot data to reduce origin read latency.
Bridges 1 incoming flow to 1 downstream dependency.
5. Primary NoSQL DB
Stores high-scale data with flexible schema and throughput.
Acts as a sink or system-of-record endpoint in the architecture flow.
6. Object Storage
Stores large files and media objects durably.
Acts as a sink or system-of-record endpoint in the architecture flow.
Tradeoffs (Latency / Availability / Cost / Complexity)
| Decision | Latency | Availability | Cost | Complexity |
|---|---|---|---|---|
| Keep the request path focused on core business operations | Shorter synchronous path keeps average response time stable | Fewer inline dependencies reduce immediate failure blast radius | Avoids unnecessary infrastructure in the first rollout | Lower coordination overhead for small teams |
| Keep a clear system of record for transactional writes | Predictable read/write behavior with indexed access | Strong correctness with managed backup and recovery | Storage and IOPS spend grows with write volume | Schema evolution and query tuning required |
| Cache hot reads in front of the primary data store | Lower median and tail latency on repeated reads | Absorbs origin pressure during read spikes | Adds cache infra spend but reduces database scaling pressure | Requires TTL and invalidation discipline |
Failure Modes and Mitigations
Failure mode: Primary datastore saturation increases latency and write timeouts
Mitigation: Tune indexes, add read offload where valid, and cap expensive query classes.
Failure mode: Cache stampede after hot-key expiry overloads the database
Mitigation: Use request coalescing, jittered TTLs, and stale-while-revalidate for hot keys.
Why This Scores Well
- Availability (35%): A compact request path limits synchronous dependencies that can fail in-line.
- Latency (20%): The design keeps hot reads close to users and reduces expensive origin round-trips.
- Resilience (25%): Clear role separation and bounded dependencies reduce cascading-failure risk.
- Cost Efficiency (10%) + Simplicity (10%): The architecture stays right-sized for the stated constraints, avoiding premature infra sprawl.
Next Step CTA
Validate this architecture by solving the prompt yourself, then practice the highest-leverage component in a guided lab and topic hub.
FAQ
What should I change first if traffic doubles?
Profile the bottleneck first, then scale the hot path component (usually compute, cache, or read path) before adding new system layers.
Why is Databases emphasized in this solution?
It is the highest-leverage topic for this challenge constraints and directly improves score-impacting metrics like latency, availability, or resilience.
How do I validate this architecture quickly?
Run the same challenge in the simulator, compare score breakdown metrics, and then test one tradeoff change at a time.
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