System Design Lab/Interactive Scenarios

Practical system-design experiments.

Step through pre-configured distributed architectures. Run real request sequences, inspect frame-by-frame state transitions, and observe how systems behave under real-world conditions.

Showing 6 scenarios

Scenario 01

16 framesBeginner

Simple Load Balancer

Round-Robin L7 Traffic Balancing

Problem Statement

How do you distribute high-volume web traffic across multiple backend servers without creating single points of failure?

What You Will Investigate

Inspect how sequential incoming HTTP requests alternate between Server 1, Server 2, and Server 3 in deterministic order.

Topology Preview

Client → Load Balancer → Server 1 / 2 / 3

Round RobinRequest RoutingTraffic Distribution

Interactive SimulatorStart Scenario →

Scenario 02

6 framesBeginner

Simple Cache (Redis + Postgres)

Cache-Aside Pattern & DB Fallback

Problem Statement

How can a system avoid hitting the primary database on every read request while maintaining cache consistency?

What You Will Investigate

Observe cache hits returning instantly from Redis memory versus cache misses that query PostgreSQL and backfill the cache.

Topology Preview

Client → Redis Cache ↔ Postgres DB

Cache AsideRedis Hit/MissDB Fallback

Interactive SimulatorStart Scenario →

Scenario 03

7 framesIntermediate

Simple API Gateway (Routing + Cache)

Unified Path Routing & Microservices Gateway

Problem Statement

How do client applications communicate with multiple microservices through a unified, secure entry point?

What You Will Investigate

Track URL path matching (/api/users/* vs /api/orders/*), downstream routing, and cached response multiplexing.

Topology Preview

Client → API Gateway → LB → Services

Path RoutingGateway ProxyMicroservices

Interactive SimulatorStart Scenario →

Scenario 04

24 framesIntermediate

Simple Valet Key (Direct Upload)

Pre-Signed Valet Keys & Storage Offload

Problem Statement

How can clients upload large multimedia files directly to cloud storage without overwhelming backend application servers?

What You Will Investigate

Step through client token negotiation, signed URL generation, and direct client-to-storage binary streaming.

Topology Preview

Client → Auth Server → Pre-Signed URL → Cloud Storage

Signed URLDirect UploadStorage Offload

Interactive SimulatorStart Scenario →

Scenario 05

14 framesIntermediate

Event-Driven Architecture (Pub/Sub Fan-Out)

Topic-Based Pub/Sub & Parallel Fanout

Problem Statement

How do you broadcast domain events across decoupled subscriber microservices asynchronously without blocking client threads?

What You Will Investigate

Watch a publisher dispatch domain events to a Pub/Sub Broker, which fans out parallel message dispatches to Email and Analytics services.

Topology Preview

Client → Publisher → Pub/Sub Broker ⇉ Email / Analytics

Pub/Sub BrokerEvent Fan-OutDecoupled Consumers

Interactive SimulatorStart Scenario →

Scenario 06

25 framesIntermediate

Message Queue & Worker Pipeline

FIFO Queue Buffering & Worker Load Leveling

Problem Statement

How can a system absorb traffic spikes and buffer resource-intensive background jobs across a pool of competing workers?

What You Will Investigate

Inspect how bursty HTTP tasks enter a FIFO Message Queue, get pulled by Worker Server 1 and 2, and commit persisted records into PostgreSQL.

Topology Preview

Client → Web Server → Message Queue ⇉ Worker 1 / 2 → Postgres

Message QueueWorker PoolPostgres Persistence

Interactive SimulatorStart Scenario →

System Design Lab/Interactive Scenarios

Practical system-design experiments.

Step through pre-configured distributed architectures. Run real request sequences, inspect frame-by-frame state transitions, and observe how systems behave under real-world conditions.

Showing 6 scenarios

Scenario 01

16 framesBeginner

Simple Load Balancer

Round-Robin L7 Traffic Balancing

Problem Statement

How do you distribute high-volume web traffic across multiple backend servers without creating single points of failure?

What You Will Investigate

Inspect how sequential incoming HTTP requests alternate between Server 1, Server 2, and Server 3 in deterministic order.

Topology Preview

Client → Load Balancer → Server 1 / 2 / 3

Round RobinRequest RoutingTraffic Distribution

Interactive SimulatorStart Scenario →

Scenario 02

6 framesBeginner

Simple Cache (Redis + Postgres)

Cache-Aside Pattern & DB Fallback

Problem Statement

How can a system avoid hitting the primary database on every read request while maintaining cache consistency?

What You Will Investigate

Observe cache hits returning instantly from Redis memory versus cache misses that query PostgreSQL and backfill the cache.

Topology Preview

Client → Redis Cache ↔ Postgres DB

Cache AsideRedis Hit/MissDB Fallback

Interactive SimulatorStart Scenario →

Scenario 03

7 framesIntermediate

Simple API Gateway (Routing + Cache)

Unified Path Routing & Microservices Gateway

Problem Statement

How do client applications communicate with multiple microservices through a unified, secure entry point?

What You Will Investigate

Track URL path matching (/api/users/* vs /api/orders/*), downstream routing, and cached response multiplexing.

Topology Preview

Client → API Gateway → LB → Services

Path RoutingGateway ProxyMicroservices

Interactive SimulatorStart Scenario →

Scenario 04

24 framesIntermediate

Simple Valet Key (Direct Upload)

Pre-Signed Valet Keys & Storage Offload

Problem Statement

How can clients upload large multimedia files directly to cloud storage without overwhelming backend application servers?

What You Will Investigate

Step through client token negotiation, signed URL generation, and direct client-to-storage binary streaming.

Topology Preview

Client → Auth Server → Pre-Signed URL → Cloud Storage

Signed URLDirect UploadStorage Offload

Interactive SimulatorStart Scenario →

Scenario 05

14 framesIntermediate

Event-Driven Architecture (Pub/Sub Fan-Out)

Topic-Based Pub/Sub & Parallel Fanout

Problem Statement

How do you broadcast domain events across decoupled subscriber microservices asynchronously without blocking client threads?

What You Will Investigate

Watch a publisher dispatch domain events to a Pub/Sub Broker, which fans out parallel message dispatches to Email and Analytics services.

Topology Preview

Client → Publisher → Pub/Sub Broker ⇉ Email / Analytics

Pub/Sub BrokerEvent Fan-OutDecoupled Consumers

Interactive SimulatorStart Scenario →

Scenario 06

25 framesIntermediate

Message Queue & Worker Pipeline

FIFO Queue Buffering & Worker Load Leveling

Problem Statement

How can a system absorb traffic spikes and buffer resource-intensive background jobs across a pool of competing workers?

What You Will Investigate

Inspect how bursty HTTP tasks enter a FIFO Message Queue, get pulled by Worker Server 1 and 2, and commit persisted records into PostgreSQL.

Topology Preview

Client → Web Server → Message Queue ⇉ Worker 1 / 2 → Postgres

Message QueueWorker PoolPostgres Persistence

Interactive SimulatorStart Scenario →

Practical system-design experiments.

Simple Load Balancer

Simple Cache (Redis + Postgres)

Simple API Gateway (Routing + Cache)

Simple Valet Key (Direct Upload)

Event-Driven Architecture (Pub/Sub Fan-Out)

Message Queue & Worker Pipeline

Loading FlowFrame...

Practical system-design experiments.

Simple Load Balancer

Simple Cache (Redis + Postgres)

Simple API Gateway (Routing + Cache)

Simple Valet Key (Direct Upload)

Event-Driven Architecture (Pub/Sub Fan-Out)

Message Queue & Worker Pipeline