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System Design
System Design
(21 posts)
ChatGPT
End-to-end: APIs, inference, memory, RAG, tools & streaming
API Gateway
auth + rate limit
Input Safety
< 50ms BERT
Context Builder
assemble prompt
Model Router
7B / 34B / 70B
GPU Scheduler
admission + priority
Conversation DB
recent + summary
User Memory
cross-conversation
RAG / Vector DB
web + files + embeds
Inference Cluster · tensor-parallel 2x A100
Prefill
compute-bound
KV-Cache
PagedAttention
Decode
memory-bound
Sample
top-p + temp
Agent / Tool Loop
web search
code sandbox
external APIs
Speculative 1.5-2x
Continuous Batching
INT4 / FP16 / FP8
3-Tier Context
System ~500
Recent ~2000
Summary ~500
Safety: 3 Layers
1. Input Classifier
2. System Prompt
3. Output Classifier
jailbreak + injection defense
Alignment Pipeline
SFT · 50K demos
Reward Model · pref pairs
DPO / PPO · optimize policy
Shadow Eval · 5% traffic
Output Safety
scan each chunk
SSE Streaming
tokens + tools + cites
User
token-by-token
persist
100M DAU
35K peak QPS
2.3T tokens / day
~1000 GPUs
P50 TTFT 1.5s
Gateway → Safety → Context Builder → Route → Schedule → Tools → Inference → Stream
Premium
System Design: ChatGPT End-to-End (Inference, Memory, RAG, Streaming, RLHF)
System Design
Jun 4, 2026 · 58 min
Maps Platform
Navigation, Routing, and Map Rendering
A
B
23 min
12.4 km via Main St
Contraction CH
S2 Cell Index
Vector Tiles
5B routes/day
50M GPS/sec
Route <1ms (CH)
500M nodes
1.2B edges
~500 nodes/query
Kafka + Flink
HMM map match
30s traffic refresh
N
Premium
System Design: Maps Platform (Navigation, Routing, and Map Rendering)
System Design
Apr 27, 2026 · 79 min
GitHub
200M repos, pull requests & CI/CD
Open
feat: add distributed cache layer
#42 opened 2 hours ago by
@kim
main
←
feat/cache-layer
All checks passed
(4/4)
build
23s
test
1m 47s
lint
12s
security-scan
34s
alice
approved
1h ago
bob
approved
20m ago
Files changed
8 files
+342
-89
Squash and merge
cache/distributed.go
+ func NewCache(opts ...Option) *Cache {
+ return &Cache{shards: 16}
+ }
// Existing code
- func oldMethod() {
- // deprecated
@alice: Consider 32 shards
for better distribution at this scale.
@bob: Add cache-hit metrics
before this lands on main.
Repository
main
feat/cache
1.2K commits
42 contributors
Source
1B git ops/day
Push -> PR -> Review -> CI -> Merge
Premium
System Design: GitHub (200M Repos, Git Object Storage, Sparse Trigram Code Search, Per-Job VM CI)
System Design
Apr 23, 2026 · 70 min
Online Auction
50K bids/sec, effectively-once settlement
Live Bid Feed
Vintage Rolex Submariner · ends in 1m 47s
j***n · $12,450
seq #847 · just now
LEADING
m***k · $12,400
seq #846 · +2m extend
EXTENDED
a***i · $12,300
seq #845 · 12s ago
OUTBID
r***l · $12,250
stale expected_price
REJECTED
CAS · Lua atomic
Bid Processor
★
Effectively-Once
Settled · Charged
Anti-Sniping
Fencing Tokens
10M auctions
1M watchers
Bids: 50K/s
Watchers: 1M
Sold today: 87K
Premium
System Design: Online Auction (50K Bids/sec, Effectively-Once Settlement, Anti-Sniping)
System Design
Apr 17, 2026 · 84 min
Job Scheduler
10M jobs/day, effectively-once execution
Task Pipeline
DAG execution with priority queues
data-pipeline-etl
attempt 1 · 25s
RUNNING
user-sync-nightly
attempt 2 · 12s
RUNNING
report-monthly
QUEUED
analytics-daily
DONE 2m ago
*/5 * * * *
Scheduler
Effectively-Once
Delivered
DAG Execution
Priority Queues
10M jobs/day
Auto Retry
Queued: 12K
Running: 4K
Done: 8.2M
Premium
System Design: Job Scheduler (10M Jobs/day, DAG Dependencies, Effectively-Once Execution)
System Design
Apr 15, 2026 · 61 min
LeetCode
50M submissions/day, sandboxed code execution
solution.py
class
Solution
:
def
twoSum
(self, nums, target):
seen = {}
for
i, num
in
enumerate
(nums):
comp = target - num
if
comp
in
seen:
return
[seen[comp], i]
seen[num] = i
1
2
3
4
5
6
7
8
Output
Accepted
Runtime: 48ms (beats 95%)
Memory: 17.2MB (beats 88%)
Test Cases: 57/57 passed
Submit
Run
Easy
1. Two Sum
Array
Hash Map
Problem
Firecracker
microVM Isolation
50M subs/day
20+ languages
CRIU Warm Pool
Anti-Cheat
Submit -> Kafka -> Firecracker Sandbox -> Judge -> WebSocket
Premium
System Design: LeetCode (Code Sandbox, Container Isolation, Real-Time Contests)
System Design
Apr 12, 2026 · 68 min
URL Shortener
10B URLs, 100K redirects/sec
Shorten your URL
https://example.com/very/long/path/to/resource?param=value&q=2
Shorten
Your shortened URL:
sho.rt/Ab3xK9f
Copy
QR
142K clicks
42 countries
68% mobile
Expires: 30d
ID Generation
Counter: 5000042
Bijective shuffle
Ab3xK9f
Encode
302 Redirect
CDN -> Valkey -> Scylla
p99 < 5ms (cache hit)
10B URLs
100K redirects/s
Base62 / 7 chars
ClickHouse
Create -> Encode -> Store -> Redirect -> Track
Premium
System Design: URL Shortener (10B Short URLs, 100K Redirects/sec)
System Design
Apr 11, 2026 · 42 min
Ad Click Aggregator
10B clicks/day, Lambda architecture & fraud detection
Click Analytics Dashboard
Last 24 hours - All campaigns
Total Clicks
847.2M
CTR
2.34%
Revenue
$4.2M
Click Volume (hourly)
0
6
12
18
24
Fraud: 2.1%
Stream (Flink)
Batch (Iceberg)
Click Events
115K/sec
10B clicks/day
Ingest
Exactly-Once
Flink checkpoints
10B clicks/day
<1min freshness
Lambda Arch
Fraud Detection
Click -> Dedup -> Aggregate -> Bill -> Reconcile
Premium
System Design: Ad Click Aggregator (10B Clicks/day, Lambda Architecture, Fraud Detection)
System Design
Data Engineering
Apr 10, 2026 · 70 min
Ad Exchange
10M auctions/sec, RTB & sub-100ms
Ad Exchange Overview
Auctions/sec
10M
DSPs
20+
Impressions
1B/day
Revenue / yr
$10B
DSP: Google DV360
Bid: $2.45 CPM
Winner
DSP: The Trade Desk
Bid: $2.12 CPM
Runner-up
DSP: MediaMath
No bid (budget cap)
Skipped
Request -> Fan-out -> Auction -> Serve
Bid Request
SSP to DSPs
Header bidding
10M auctions/s
Sub-100ms
OpenRTB 2.6
First-Price
Premium
System Design: Ad Exchange (Real-Time Bidding, Sub-100ms Auctions, DSP/SSP, Impression Serving)
System Design
Apr 10, 2026 · 59 min
Flash Sale
10M users, limited coupons, one-per-user
FLASH SALE - Up to 70% OFF
Limited Stock! Ends in:
02:34:12
Wireless Earbuds
$99
$29
-70%
12 left!
Smart Watch
$149
$59
-60%
58 left
Bluetooth Speaker
SOLD OUT
USB-C Hub
$79
$39
-50%
142 left
SAVE20
Extra 20% off
Apply
One coupon per user - 500K available
Buy Now - $29
Queue
#2,431
of 10M users
~4 min wait
Waiting Room
10M users
500K coupons
Lua DECR
SET NX 1/user
Queue -> Browse -> Coupon -> Pay -> Confirm
System Design: E-Commerce Flash Sales (10M Users, Coupon System, One-Per-User Enforcement)
System Design
Apr 5, 2026 · 107 min
News Aggregator
100K sources, dedup & personalization
News Aggregator Overview
Sources
100K
Articles/day
5M
Unique
2M
Users
50M
reuters.com
Earthquake in Japan
Breaking
bbc.co.uk
Election results update
Trending
techcrunch.com
AI startup raises $50M
Tech
Crawl -> Dedup -> Rank -> Personalize
RSS Polling
Adaptive frequency
5min to 6hr
100K sources
MinHash LSH
Adaptive Poll
Decay Ranking
Premium
System Design: News Aggregator (100K Sources, Dedup, Personalized Ranking)
System Design
Apr 5, 2026 · 87 min
Dropbox
File sync, chunking & deduplication
report.xlsx · 100 MB · 8 chunks
C1
sha:a3f2..
C2
sha:b7e1..
C3'
sha:NEW!
C4
sha:d9c4..
C5
sha:e2a8..
C6
sha:f1b3..
C7
sha:0c7d..
C8
sha:4e9f..
upload 4 MB
7 chunks unchanged · skip · saved 96 MB
Edit
!
Chunk + Delta
✓
✓
✓
Sync
500M
users
100 PB
storage
<10s
cross-device sync
50%
dedup savings
Edit file. Upload only what changed. Sync everywhere.
presigned URLs · bytes skip the server · CDC or rsync
Premium
System Design: Dropbox (File Sync, Chunking, and Deduplication)
System Design
Apr 2, 2026 · 69 min
Object Storage
Store anything, retrieve anytime, lose nothing
11 Nines Durability
1.4x Overhead
Strong Consistency
100T+ Objects
Exabyte Scale
350K req/sec
PUT anything. GET anytime. Never lose a byte.
photos/2024/beach.jpg
Premium
System Design: Object Storage (Erasure Coding, Flat Namespace, and Exabyte Scale)
System Design
Mar 31, 2026 · 54 min
AI Software Engineer
From autocomplete to autonomous app builder
L1: AUTOCOMPLETE
300ms
12
async
function
getUser
(id) {
13
const user =
await db.find(id)
14
if (!user) throw
Tab ↵
Context + FIM + Ranking
90M completions/day
L2: CODEBASE AGENT
45 sec
search_files("authenticate")
✓ 8 files
read_file("src/auth/session.ts")
✓ 142 lines
edit_file("src/middleware/auth.ts")
✓ applied
run_command("npm test")
✓ 48 pass
12 files edited, all tests pass
Think → Act → Observe → Repeat
1.5M agent sessions/day
L3: AI ENGINEER
4 hours
DB Schema
Done
Auth Module
Done
Kanban Board
In Progress
Stripe Billing
Queued
Deploy to Vercel
Queued
Step 120 / 200 (60%)
Checkpoint cp-120
Memory: CLAUDE.md
Spec → Build → Test → Deploy
50K build sessions/day
Model 50% | System 50%
Model 25% | System 75%
Model 10% | System 90%
L1: Autocomplete
L2: Agent
L3: Autonomous
Keystroke → Context → Model → Verify → Ship
Premium
System Design: AI Software Engineer (From Autocomplete to Autonomous App Builder)
System Design
AI
Mar 25, 2026 · 94 min
RAG & LLM Platform
From Documents to Accurate, Cited Answers at Scale
Ingest
2M+ documents
Chunk & Embed
10M vectors
Retrieve
Hybrid + Re-rank
Generate
Routed + Cited
Evaluate
LLM-as-Judge
Continuous Improvement Loop
RAG and LLM Platform at Scale: Ingestion, Retrieval, Generation, and Evaluation for 10M Queries/Day
System Design
AI
Mar 22, 2026 · 105 min
AI Agent Platform
Restaurant operations intelligence at scale
Detect
Investigate
Act
DATA IN
POS Systems
Toast · Square · Clover
Delivery
DoorDash · Uber Eats · Grubhub
Payments
Stripe · Adyen
Inventory
MarketMan · BlueCart
Agent
Agent
Agent
Agent
ACTIONS OUT
Alerts
SMS · Email · Dashboard
Reports
Root cause analysis
Auto-Fix
Disputes · Reorders · Pauses
Insights
Trends · ROI · Recommendations
KAFKA · FLINK · CLICKHOUSE · TEMPORAL · LLM AGENTS
10K investigations/day · Multi-tenant · Real-time anomaly detection
Premium
Building a Multi-Tenant AI Agent Platform for Restaurant Intelligence
System Design
AI
Mar 17, 2026 · 109 min
Collaborative Editor
Real-time editing with CRDTs
B
I
U
Alice
Bob
Carol
A
Alice
B
Bob
C
Carol
CRDT (Yjs)
Offline-first
100 editors/doc
<100ms sync
originLeft
originRight
merge(A,B) = merge(B,A)
WebSocket
bidirectional
binary sync
System Design: Real-Time Collaborative Editor
System Design
Mar 14, 2026 · 86 min
Observability Platform
Metrics, Traces, Logs, and Profiles at Scale
SLO 99.9%
ML
eBPF + OTel → Pipeline → Kafka → Processing → Storage → Query
Traces
Profiles
Logs
Grafana
500M metrics/s
200M spans/s
50M log lines/s
50K profiles/s
p99 < 200ms
4 signal types
tail sampling
eBPF + OTel SDK
Premium
Observability Platform at Scale - Metrics, Traces, Logs, and Profiles
System Design
Mar 12, 2026 · 115 min
Notification System
100M/sec across every channel
Web
Mobile
Wearable
p99 < 500ms
99.99% up
100M connections
3 channels
Premium
System Design: Notification Platform, 100M Notifications/Second
System Design
Mar 6, 2026 · 79 min
Top-K Streaming
What's trending right now?
1
2
3
4
5
1.5M
980K
720K
410K
290K
LIVE
updated 12s ago
Premium
Building a Fail-Safe, Scalable Top-K Streaming System
System Design
Data Engineering
Feb 27, 2026 · 51 min
Tagging System
Multi-tenant, globally consistent
Spanner
US
Redis + Kafka + ES
EU
Redis + Kafka + ES
Asia
Redis + Kafka + ES
#marketing
#design
#api
#docs
#sales
#launch
#v2
#infra
CONSISTENT
across 3 regions
Premium
Designing a Multi-Tenant, Globally Scalable Tagging System
System Design
May 25, 2025 · 23 min