# hw1：短網址系統設計
>請你畫出一張短網址服務的後端系統架構圖，越詳細越好，可以考慮到如何增進效能、scaling 以及備份資料。

>[短网址(short URL)系统的原理及其实现](https://hufangyun.com/2017/short-url/)
>

digraph graphname{
r [label="request URL"]
lb [label="Load Balace"]
s1 [label="Server 1"]
s2 [label="Server 2"]
dbs [label="DB Slaves"]
dbm [label="DB Master"]
end [label="return tiny url",shape=box]
s[label="store new url" ,shape=box];
g[label="generate a new tiny url",shape=box];
c[label="cache"];
note[label=" ... same process with server 1", shape=box];

//[label=""]
    r->lb[color="blue"];
    r->lb;
    lb->s1;
    lb->s2[color="blue"];
    s1->c;
    s2->c[color="blue"];
    c->s2[color="blue"];
    c->s1;
    s2->note[color="blue"];
    s1->dbs[label=" read"];
    dbs->end[color=green, label="record found"];
    dbs->s1[label="return'Not found'",color=red];
    s1->s[color=red];
    s->dbm[color=red];
    s1->g[color=red];
    g->dbm[color=red];
    g->end[color=red];
    c->end[color=green];
}