System Design · Deep Dives

Design systems beyond the whiteboard.

Interview-depth case studies where every decision is justified. Built as a progression — start from first principles, climb to distributed systems.

Concepts
Core Concepts
Availability, reliability, scalability, CAP theorem, consistency models, fault tolerance, PACELC.
Storage & Databases
ACID, indexing, sharding, replication, database types, data modeling, CDC, pagination.
Caching
Write strategies, eviction policies, cache invalidation, distributed caching, Redis, cache problems.
Messaging & Event Driven
Kafka, SQS, RabbitMQ, event sourcing, CQRS, outbox pattern, stream & batch processing.
Back of Envelope Estimation
Latency Numbers
Every number you need to know — memory, disk, network.
Database Numbers
Read/write throughput, storage sizes, query costs.
Message Streams
Kafka throughput, queue sizing, consumer lag.
Estimation Framework
A reusable framework for any system design estimation.
Apply the Concepts — Case Studies
01
Foundation ● ○ ○ ○ ○

First principles of scale

Unique ID schemes, sharding strategies, read-heavy caching, hot key mitigation, pre-generated key pools, tiered storage.

Snowflake ID UUID Clock skew Consistent hashing Bloom filters KGS Hot key problem Cold storage
Start →
02
Ascent ● ● ○ ○ ○

Async pipelines & multi-channel delivery

Kafka fan-out, per-channel workers, retry/DLQ, scheduled dispatch, content deduplication, async uploads, expiry at scale.

Kafka fan-out Retry / DLQ Bloom filter Circuit breaker Content-addressable storage Async S3 upload TTL sweeper Watchdog
Open →
03
Expedition ● ● ● ○ ○

Distributed rate control

Rate limiting algorithms from scratch, atomic Redis counters, distributed enforcement, rule management, DDoS layered defence.

Token bucket Leaky bucket Sliding window Fixed window Lua atomicity Redis cluster DDoS defence
Open →
04
Summit ● ● ● ● ○

Storage engine internals

Leaderless replication, quorum reads/writes, LSM tree internals, compaction strategies, gossip membership, conflict resolution.

LSM trees Compaction Bloom filters Quorum W/R Gossip protocol Hinted handoff Vector clocks Anti-entropy
Open →
05
Battleground ● ● ● ● ●

Real-time systems at scale

WebSocket connection management, per-conversation sequencing, offline queues, thundering herd, backpressure, hot partition salting.

WebSockets Per-conv. sequencing Offline delivery Thundering herd Backpressure Hot partition salting Reconnect storm Read receipts
Open →

Each case study is a progression: requirements → estimation → base architecture → deep dives → final design → observability. Read top-to-bottom, or jump straight to the deep dive you want.