Design systems that actually scale
An interview-focused path through the concepts every senior-track interview loop tests — scalability, databases at scale, caching, distributed systems, microservices, security and low-level design — through five full worked case studies and ending in a mock design-interview capstone you can rehearse out loud.
Prerequisites & tooling
What you should already know
- Comfortable programming in at least one language
- Basic familiarity with databases and APIs — this course builds the "why," not the syntax
- No prior system design or distributed systems background required
- Pairs naturally with DSA in C++ for a complete interview-prep track
Concepts you'll work with
The same vocabulary and tradeoffs tested in mid-to-senior system design interview rounds.
Your 28-week learning path
Twenty-four modules, from your first back-of-envelope estimate through five full case studies to a mock design interview.
System Design Fundamentals & Requirements Gathering
The estimation and scoping skills every design question starts with.
- Functional vs. non-functional requirements & scope framing
- Back-of-envelope estimation: throughput, storage & bandwidth math
- Reading and drawing a basic system architecture diagram
Networking & APIs for System Design
The request path every architecture diagram assumes you understand.
- IP, DNS, load balancers & the request/response path
- REST vs. gRPC vs. GraphQL — when each earns its complexity
- CDNs & edge caching for static and dynamic content
Scalability Fundamentals
Grow a system past what one machine can handle.
- Vertical vs. horizontal scaling & stateless service design
- Load balancing algorithms: round robin, least connections & consistent hashing
- Failure modes: thundering herd & hot partitions
Databases at Scale
Choose and shape a data layer that survives real load.
- SQL vs. NoSQL: choosing the right data model
- Indexing strategies & read/write tradeoffs
- Replication, sharding & partitioning strategies
Caching & Content Delivery
Make the common case fast without lying to the user.
- Cache-aside, write-through & write-behind strategies
- Redis/Memcached patterns & eviction policies
- Cache invalidation in practice — the "two hard problems" made concrete
Message Queues & Asynchronous Processing
Decouple producers from consumers instead of chaining synchronous calls.
- Pub-sub vs. point-to-point messaging (Kafka vs. RabbitMQ/SQS)
- Decoupling producers & consumers with a queue
- At-least-once vs. exactly-once delivery & idempotency
Distributed Systems & Consistency
The tradeoffs behind every "it depends" answer in a design interview.
- The CAP theorem & what it actually constrains
- Consistency models: strong, eventual & causal consistency
- Leader election & consensus (Raft/Paxos) at a conceptual level
Rate Limiting & API Gateway Patterns
Protect a system from its own clients.
- Token bucket, leaky bucket & sliding window algorithms
- API gateway responsibilities: auth, routing & throttling
- Designing a distributed rate limiter
Low-Level Design: OOP & Design Patterns
The class-design half of a system design loop.
- SOLID principles applied to interview-style LLD questions
- Strategy, Observer, Factory & Singleton in real designs
- Designing a class model for a parking lot / elevator system
Case Study I: Design a URL Shortener & Rate Limiter
Your first full design, start to finish, at interview scope.
- Requirements, estimation & API design for a URL shortener
- Choosing a data store & encoding strategy
- Layering in the rate limiter from Week 11
Case Study II: Design a Large-Scale System
Combine every module into one senior-level design.
- Designing a news feed / social platform at scale
- Fan-out on write vs. fan-out on read
- Combining caching, queues & sharding into one coherent design
Microservices Architecture & Service Decomposition
When to split a monolith, and how to draw the boundaries so it doesn't backfire.
- When to split a monolith, with concrete criteria
- Decomposing by bounded context, not by technical layer
- Sagas for cross-service consistency
Service Mesh, API Gateways & Inter-Service Communication
Wire decomposed services back together without building a distributed monolith.
- API gateway vs. service mesh, and the sidecar pattern
- Service discovery across scaling instances
- Circuit breakers & retries to stop cascading failure
Observability — Logging, Metrics & Distributed Tracing
Make a distributed system's behavior legible from the outside.
- The three pillars: logs, metrics & traces
- Structured logging & the RED/USE metrics frameworks
- Distributed tracing across service boundaries
Security in System Design
AuthN vs. AuthZ, encryption, secrets, and designing for active abuse.
- Authentication vs. authorization at scale
- Encryption in transit & at rest, and secrets management
- Designing a layered defense against DDoS
Search Systems & Full-Text Search
The inverted index, relevance ranking, and low-latency autocomplete.
- Why a normal database index can't power full-text search
- The inverted index & TF-IDF/BM25 relevance ranking
- Autocomplete/typeahead with a precomputed trie
Real-Time Systems — WebSockets, Presence & Pub/Sub at Scale
Push updates to clients live, and scale stateful connections across many servers.
- WebSockets vs. long polling vs. Server-Sent Events
- Online/offline presence with a tuned heartbeat
- Pub/sub fan-out across stateful connection servers
Distributed File & Object Storage
Chunking, storage tiers and durability at the scale of billions of files.
- Object vs. block vs. file storage
- Chunking large files & resumable uploads
- Replication vs. erasure coding for durability
Geo-Distributed Systems & Multi-Region Architecture
Serve users worldwide and survive a full regional outage.
- Active-active vs. active-passive architecture
- Cross-region replication lag & conflict resolution
- Designing a regional failover plan
Consensus & Coordination Services
Leader election, distributed locks and split-brain, made concrete.
- How leader election actually works, mechanically
- Distributed locks & the fencing-token fix
- The split-brain problem & coordination services in practice
Case Study III: Design a Ride-Sharing Dispatch System
Geospatial indexing, a live location stream, and matching without double-booking.
- Estimating a system dominated by location pings, not user actions
- Geohashing for efficient nearby-driver search
- Matching with a distributed lock, safely
Case Study IV: Design a Video Streaming Platform
The upload-to-playback pipeline and a storage strategy for a long-tail view distribution.
- The asynchronous transcoding pipeline
- Adaptive bitrate streaming, explained
- Storage & CDN tiering by access pattern
Case Study V: Design a Distributed Chat System
Delivery guarantees, group fan-out, and message history at scale.
- Exactly-once, in-order delivery with sequence numbers
- Group chat fan-out that scales past 500 members
- Message storage & fast, paginated history
Capstone: Full System Design Interview Simulation
Put every module to work as one real, rehearsable interview performance.
- A complete written design doc for one large system, end to end
- Diagrams, capacity estimates & explicit tradeoff analysis
- A mock interview script you can rehearse out loud