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Reference & domain model

26 frameworks · 77 scenarios · 13 operational patterns · 7 deployment patterns — a reference for everything you can manipulate in the simulator.

Getting started

Intro
What serversim is — and what it is not
5-min quickstart
Run your first scenario and tweak knobs
Core concepts
CPU / waiting / threads / event loop / coroutines

Framework catalog

Web Server
NGINX
CDN
Edge cache (PoP, origin fetch)
Load Balancer
HAProxy (roundrobin / leastconn / source)
Auth / SSO
Keycloak (OAuth2, JWT cache, MFA)
Application
Spring Tomcat/WebFlux / FastAPI / Express / Django
Database
MySQL / PostgreSQL / MongoDB / Cassandra / CockroachDB
Vector DB
pgvector (HNSW / IVF, RAG)
Cache
Redis / Memcached
Message Broker
Kafka / RabbitMQ / Redis Streams
Stream Processing
Apache Flink (stateful, exactly-once)
Search & Index
Elasticsearch
Analytics (OLAP)
ClickHouse
Object Storage
Object Storage (HTTP)
Workflow
Temporal (durable workflow)
Observability
Prometheus (TSDB)

Operational patterns

Circuit Breaker
Resilience4j-style (closed / open / half-open)
Retry + Backoff
exponential + jitter, paired with CB
Bulkhead
Isolated concurrent calls (semaphore)
Client Timeout
RestTemplate.readTimeout model
HPA Auto-scaling
CPU threshold + cooldown
Rate Limit
NGINX limit_req token bucket
Health Probe
Readiness + failure threshold
Sidecar (Service Mesh)
Envoy / Linkerd, mTLS
DB Replication
Primary / replica + dynamic lag
Outbox Pattern
DB write + broker publish atomically
CQRS
Command / query separation
Saga (choreography / orchestration)
Distributed transactions
Hot Key Lock
DB row-level serialization

Deployment patterns

Rolling Update
K8s default, 25% step
Canary
10% v2 + automated Flagger-style gate
Blue-Green
LB switch + DB migration safety
Shadow
LB mirror + drop response
A/B Test
50/50 split + business metric
Feature Flag
Deploy ≠ release
Dark Launch
v1 response + async v2 compare

Scenario categories

Featured
8 featured scenarios
Basics
3-tier / cached / GC / pool
Interview classics
URL shortener / chat / video / mobility / social feed + Saga / CQRS / Outbox
Pitfalls
"just add more servers?" — 6 traps
Ops patterns
Canary / Blue-Green / Rolling / Shadow / A-B / Feature flag
Large-scale / distributed
Multi-region / sharded / ELK / OLAP / CDN
Broker
Kafka / RabbitMQ / Redis Streams
Evolution
MVP → cache + replica → async

All frameworks / scenarios / patterns are interactive inside the simulator. Open the Library modal to browse by category.

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