System Design Cheat Sheet

Reference: Tech Dummies , System Design, Netflix, GeeksForGeeks

For you to go through just before the interview :).

Disclaimer: This article is still under work. Still have to add notes and more architecture designs. Feel free to add comments on what else to add.

Load Balancers (LB)

Selects Servers/Databases/Caches following some algorithm

1. Round Robin: Select servers one after another
2. Weighted Round Robin: Admin assigns weight, i.e. probability of getting selected. Server 1 with twice weight of Server 2 will be allotted twice as many requests.
3. Least Connection/Response Time/ Resource Based: Dynamic Load balancing. Server with Least Connection/Response Time/ Resource Based is allotted next request. The values are calculated using client installed at servers.
4. Similarly we have Weighted flavor of Least Connection/Response Time/ Resource Based.

Types: (Ex AWS)

• L4 : Makes balancing decision only on IP address , tcp port. Cannot see request header, client, type etc.
• L7 : Has info about url, message, request type, header, client everything. Can route request based on type of request

Use L4 when you need to make simple reliable and fast balancing decision on server load, which has reliable TCP connection. Use L7 when you need to route request to appropriate resource server, such as…