Active: News feed (interview scale)
✕
✕
Client
BROWSER / MOBILE
↕ 120k/s
Web and mobile users sending reads and writes.
CDN
EDGE CACHE
Caches static assets at the edge so they never hit your servers.
Load Balancer
NGINX / HAPROXY
Spreads incoming traffic across the gateway so no one box is overwhelmed.
API Gateway
GATEWAY / PROXY
Front door: routing, auth, and rate limiting. Scales out behind the load balancer.
App Server×3
AUTOSCALING
56%
Handles new posts; publishes them to the queue for fan-out.
App Server×3
AUTOSCALING
56%
Builds each user's feed; reads are cached, writes go async.
App Server×3
AUTOSCALING
56%
Profiles and accounts; reads from cache or replica, writes to the primary.
App Server×3
AUTOSCALING
56%
Handles uploads; blobs to object storage, metadata to the database.
App Server×3
AUTOSCALING
56%
Answers search queries from the index; indexing runs async.
WebSocket Server×3
WS / SSE
67%
Holds live WebSocket connections to push updates to clients.
Cache×3
REDIS 7
Serves the hottest reads from memory, sparing the database.
SQL Database
POSTGRES 15
59%
The single write database. Unscalable, so it is the ceiling under load.
Message Queue
KAFKA / SQS
Buffers writes so services reply instantly; workers drain it later.
Search Index×2
ELASTICSEARCH
Search index: fast text queries the database cannot do.
Read Replica×3
STREAMING REPL
Read-only copies; soak up read misses so the primary only writes.
Worker
CONSUMER GROUP
Workers that drain the queue and write results into the database.
Object Store
S3 / BLOB
Stores large blobs (images, video) cheaply, outside the database.
✕
Select a source to raise or lower the simulated load.
p9538ms
errors0.0%
HoldsStable at 120k req/s.
Components · drag onto the canvas
edge
Client
BROWSER / MOBILE
Where requests come from. Sets the load on everything downstream.
DNS
ROUTE 53
Turns a domain name into an address. Heavily cached, so almost free.
CDN
EDGE CACHE
Serves static files (images, video) from the edge, close to the user.
net
Load Balancer
NGINX / HAPROXY
Spreads traffic across many servers so no single one is overwhelmed. Scales out horizontally.
API Gateway
GATEWAY / PROXY
Routing, auth, and rate limiting before your servers. Scales out behind the load balancer.
compute
App Server
AUTOSCALING
Application logic tier. Stateless: scale out behind a load balancer.
Worker
CONSUMER GROUP
Drains a queue and does slow work in the background, off the request path.
realtime
WebSocket Server
WS / SSE
Holds persistent live connections (WebSocket/SSE) and pushes updates the instant they happen.
cache
Cache
REDIS 7
Remembers hot reads so the database is not asked the same thing twice.
data
SQL Database
POSTGRES 15
The source of truth. One primary handles writes; the usual bottleneck.
NoSQL Database
DYNAMO / CASSANDRA
Sharded store. Scales reads and writes by key, at the cost of joins.
Read Replica
STREAMING REPL
Read-only copy of the primary. Reads scale out; writes stay on the primary.
Shard
PARTITION
One slice of the data, split by key. Add shards to scale writes.
Search Index
ELASTICSEARCH
Full-text search over your data. Fed from the database, queried for search.
queue
Message Queue
KAFKA / SQS
Buffers writes so the server replies fast and workers catch up at their pace.
store
Object Store
S3 / BLOB
Cheap, huge storage for big blobs: images, video, backups. Not for queries.
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