SD: Load Balancers

content/posts/load-balancers.md

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+title = 'SD: Load Balancers'
+date = 2024-10-08T21:53:16-06:00
+draft = false
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+
+Load Balancers (LB) are a crucial component for System Design. They are basically in charge of distributing incoming requests and traffic _evenly_ across multiple servers while avoiding the overload and downtime of servers.
+
+## Good places to put a LB
+
+- Between user and web servers
+- Between web servers and internal platform layer
+- Between platform layer and databases
+
+## How does a request get processed by a Load Balancer?
+
+- Request is received
+- Request then is evaluated:
+  - LB determines which server or resource should handle the request
+    - At this point, the Load Balancer Algorithm takes into account the following things:
+      - Server capacity and response time
+      - Number of active connections
+      - Geographic location
+
+- LB forwards request to the server
+- Server responds back to the LB
+- LB processes response and sends it back to the user/client
+
+## Load Balancer Algorithms
+
+The algorithms listed here will be a good option in particular scenarios.
+
+In general, these algorithms will ensure efficient utilization of available resources, improve overall system performance and maintain high availability and reliability.
+
+### Round Robin
+
+Assigns incoming requests to servers in a cyclic order by following the [Round Robin technique](https://en.wikipedia.org/wiki/Round-robin_item_allocation).
+
+#### Uses
+
+- Suitable for environments where _**all servers have similar capacity and performance**_
+- Good option for _**stateless**_ applications where each request can be handled independently
+
+### Least Connections
+
+Assigns incoming requests to the server with fewest active connections at the time of the request
+
+#### Uses
+
+- Suitable for environments where _**servers have different capacity and workload**_
+- Good option for _**stateful**_ applications where maintaining the session state is mandatory
+- When traffic is highly variable and unpredictable