Concepts

System design building blocks

Short learning notes for the concepts, tools, services, and techniques that shape architecture decisions.

Paths

Start with a path

System Design Foundations

The vocabulary and mental models behind every architecture diagram.

Load Balancer API Gateway Message Queue Object Storage

Data & Storage Basics

How systems store, find, copy, and keep data consistent.

Cache-Aside Write-Through Cache Sharding Replication

Real-Time Systems

Patterns for low-latency messaging, collaboration, and live updates.

WebSocket Pub/Sub Backpressure CRDT

Reliability & Scaling

The tools that keep distributed systems available under stress.

Rate Limiting Circuit Breaker Retry with Exponential Backoff Eventual Consistency

Security Architecture

Core protocols and controls for identity, privacy, and transport safety.

OAuth2 Authorization Code Flow JWT TLS

AI Infrastructure

The building blocks behind modern LLM and retrieval systems.

GPU Inference Embeddings Vector Database

Browse

All concepts

FoundationsFoundational4 min

API Gateway

A controlled front door for authentication, routing, rate limits, and API policy.

APIgatewayroutingauth

ReliabilityIntermediate4 min

Backpressure

Slow producers down when consumers cannot keep up.

backpressurequeuesstreamingreliability

Data & StorageAdvanced4 min

Bloom Filter

Quickly test whether an item is definitely absent or maybe present.

Bloom filterprobabilisticcachedata

Data & StorageFoundational4 min

Cache-Aside

Let the application read through the cache and repopulate missing data on demand.

cachingRedisinvalidationperformance

Cloud & InfraFoundational4 min

CDN

Cache and serve content close to users so origin systems stay fast and protected.

CDNcachingedgeperformance

ReliabilityIntermediate4 min

Circuit Breaker

Stop calling an unhealthy dependency before failures cascade through the system.

circuit-breakerresiliencefailuresreliability

Architecture TechniquesAdvanced5 min

CRDT

Let distributed replicas accept local edits and merge without conflicts.

CRDTcollaborationconflict-resolutionreal-time

ObservabilityIntermediate4 min

Distributed Tracing

Follow one request across services, queues, databases, and external calls.

tracingobservabilitylatencymicroservices

AI/ML InfraIntermediate4 min

Embeddings

Represent text, images, users, or items as vectors that capture semantic similarity.

embeddingsvectorssearchrecommendation

Data & StorageIntermediate4 min

Eventual Consistency

Allow replicas to temporarily disagree while guaranteeing they converge later.

consistencyreplicationdistributed-systemsavailability

AI/ML InfraAdvanced5 min

GPU Inference

Run trained models efficiently enough to serve user requests in real time.

GPUinferenceLLMAI

ReliabilityFoundational4 min

Idempotency

Make repeated requests safe so retries do not create duplicate side effects.

idempotencyretriesreliabilityAPI

SecurityFoundational4 min

JWT

A signed JSON token that carries claims between systems.

JWTauthtokenssecurity

FoundationsFoundational4 min

Load Balancer

Distribute traffic across healthy servers without making clients know where work runs.

load-balancerroutingavailabilityedge

FoundationsFoundational4 min

Message Queue

Buffer work between producers and consumers so systems can absorb spikes and retry safely.

queueasyncjobsreliability

SecurityIntermediate5 min

OAuth2 Authorization Code Flow

Let users grant access without giving your app their password.

OAuth2authsecuritylogin

Data & StorageFoundational4 min

Object Storage

Store large immutable blobs behind keys instead of rows and file paths.

object-storagefilesmediaS3

ObservabilityFoundational4 min

Observability

Understand what a production system is doing from its external signals.

observabilitymetricslogstracing

Architecture TechniquesAdvanced5 min

Operational Transform

Transform concurrent edits so collaborative documents preserve user intent.

OTcollaborationreal-timedocuments

Real-TimeFoundational4 min

Pub/Sub

Broadcast events from publishers to many independent subscribers.

pub-subeventsfan-outreal-time

ReliabilityFoundational4 min

Rate Limiting

Control request volume so shared systems stay fair, stable, and protected.

rate-limitingAPIRedisprotection

Data & StorageFoundational4 min

Replication

Copy data across nodes to improve availability, read scale, and disaster recovery.

replicationdatabaseavailabilityconsistency

ReliabilityFoundational4 min

Retry with Exponential Backoff

Retry transient failures slowly enough that recovery is possible.

retriesbackoffreliabilityfailures

Data & StorageFoundational4 min

Search Index

Precompute searchable structures so users can find data quickly.

searchindexElasticsearchdata

ScalabilityIntermediate5 min

Sharding

Split a dataset across machines so storage and traffic can scale horizontally.

shardingdatabasescalabilitypartitioning

Data & StorageIntermediate4 min

Strong Consistency

Make reads reflect the latest committed write for correctness-critical data.

consistencytransactionsdatabasecorrectness

SecurityFoundational4 min

TLS

Encrypt and authenticate network connections between clients and services.

TLSencryptioncertificatessecurity

AI/ML InfraIntermediate4 min

Vector Database

Store embeddings and retrieve nearest neighbors at scale.

vector databaseembeddingssearchAI

Real-TimeFoundational4 min

WebSocket

Keep a bidirectional connection open for low-latency client and server messages.

WebSocketreal-timemessagingpresence

Data & StorageIntermediate4 min

Write-Through Cache

Keep cache and database updated together so reads can trust the cached value.

cachingconsistencyRedisdatabase