The Story About Cache

charsyam@naver.com

Use Case: Login

Use Case: Login

Common Case

Use Case: Login

Common Case Read From DB

Select * from Users where id=‘charsyam’;

Use Case: Login

May be it’s genenally fast

Use Case: Login

But it’s Slow In Many Read/Write

Use Case: Login

Advanced Case Read From Cache

Get charsyam

Use Case: Login

it’s always fast

Use Case: Login

136 vs 1613 seconds

Memcache VS Mysql

Use Case: Login

250 million User ID Request 10 million

Where We Can Use Cache?

Just Check User exists? Mail Receive, Tweet Mention

Get User’s Profile Get User’s Timeline

Caches

Memcache

Redis

Memcache

Atomic Operation

Memcache

Atomic Operation

Key:Value

Memcache

Atomic Operation

Key:Value Single Thread

Memcache

Over 100,000 TPS Processing

Redis

Key:Value

Redis

Key:Value

Collection

List Sorted Set

Cache Layer

Cache

DBMS

Storage Layer

Application Server

READ

WRITE

WRITE UPDATE

Cache Layer Like Twitter

K: UserID, V: Y/N

K: UserID_TIMELINE, V: Tweet IDs

K: UserID_TWEETID, V: Tweet Contents

Check User exists

Check tweet list

Check Content

1st Level Cache

2nd Level Cache

3rd Level Cache

BUTs

Sometimes Cache is slower than DB

Why?

DBMS Also Uses Cache If Cache is hit. It’s faster than …

DBMS

DBMS

Storage Layer

Application Server

READ

WRITE

Cache

Environment

Small Data Sets Read Just 0.2~03mili

Comparision

DB’s Cache: 0.2mili memCache: 0.4mili

If you check cache, you spend more time

BUTs BUTs

Cache helps to reduce DBMS’s Loads

And It reduces Performance Deviation

Use Cache!

Thank you!