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System Design
HLD concepts · LLD patterns · Design problems — all in one place
HLD Concepts
LLD Concepts
Problems
All
Fundamentals & Core Concepts
Scalability
Databases
Caching
Messaging & Event-Driven Systems
APIs & Communication
Search
Storage & File Systems
Security & Auth
Observability
Distributed Systems Concepts
Reliability & Fault Tolerance
Infrastructure & Deployment
55 concepts
01
Client-Server Architecture
Fundamentals & Core Concepts
02
Monolith vs Microservices
Fundamentals & Core Concepts
03
Synchronous vs Asynchronous Communication
Fundamentals & Core Concepts
04
Latency vs Throughput vs Availability
Fundamentals & Core Concepts
05
CAP Theorem
Fundamentals & Core Concepts
06
PACELC Theorem
Fundamentals & Core Concepts
07
SLA / SLO / SLI
Fundamentals & Core Concepts
08
Horizontal vs Vertical Scaling
Scalability
09
Load Balancing (L4 vs L7)
Scalability
10
Auto-scaling Strategies
Scalability
11
Stateless vs Stateful Services
Scalability
12
SQL vs NoSQL
Databases
13
Database Sharding & Partitioning
Databases
14
Replication (Master-Slave, Master-Master)
Databases
15
Indexing Strategies
Databases
16
ACID vs BASE Properties
Databases
17
Consistent Hashing
Databases
18
Cache Strategies (Write-through, Write-back, Write-around)
Caching
19
Cache Eviction Policies (LRU, LFU, TTL)
Caching
20
Distributed Caching (Redis, Memcached)
Caching
21
Cache Invalidation Strategies
Caching
22
Cache Stampede / Thundering Herd
Caching
23
Message Queues (RabbitMQ, SQS)
Messaging & Event-Driven Systems
24
Event Streaming (Kafka, Kinesis)
Messaging & Event-Driven Systems
25
Pub/Sub Pattern
Messaging & Event-Driven Systems
26
Exactly-once vs At-least-once Delivery
Messaging & Event-Driven Systems
27
Event Sourcing & CQRS
Messaging & Event-Driven Systems
28
REST vs GraphQL vs gRPC
APIs & Communication
29
API Gateway
APIs & Communication
30
Rate Limiting & Throttling
APIs & Communication
31
Webhooks vs Polling vs SSE vs WebSockets
APIs & Communication
32
Full-text Search (Elasticsearch)
Search
33
Inverted Index
Search
34
Typeahead / Autocomplete Design
Search
35
Object Storage (S3, GCS)
Storage & File Systems
36
Block vs Object vs File Storage
Storage & File Systems
37
Large File Upload Strategies
Storage & File Systems
38
Authentication vs Authorization
Security & Auth
39
OAuth 2.0 / OpenID Connect / JWT
Security & Auth
40
TLS / HTTPS
Security & Auth
41
Logging (Structured & Centralised)
Observability
42
Metrics & Monitoring (Prometheus, Grafana)
Observability
43
Distributed Tracing (Jaeger, OpenTelemetry)
Observability
44
Health Checks & Circuit Breaker
Observability
45
Consensus Algorithms (Raft, Paxos)
Distributed Systems Concepts
46
Distributed Locks (Redlock)
Distributed Systems Concepts
47
Saga Pattern (Distributed Transactions)
Distributed Systems Concepts
48
Idempotency
Distributed Systems Concepts
49
Retry with Exponential Backoff
Reliability & Fault Tolerance
50
Graceful Degradation
Reliability & Fault Tolerance
51
Disaster Recovery (RPO & RTO)
Reliability & Fault Tolerance
52
Docker & Kubernetes Basics
Infrastructure & Deployment
53
Blue-Green / Canary Deployments
Infrastructure & Deployment
54
Reverse Proxy (NGINX)
Infrastructure & Deployment
55
Service Mesh (Istio)
Infrastructure & Deployment