Proxy

Proxy is a dedicated computer or software system running in the same computer or different computer acts as intermidiary between the requester of a website and the actual web server.
Type of proxy:
• Forward Proxy: it helps in connecting the user to the website.
• Reverse Proxy: it is used:

o To allow load balancing between the server.
o To stream internal content to its user. (SSO page)
o To block some particular website.
Nginx 

Load balancers:

• With the many servers configured as upstreams, you can define proxy_pass to this upstreams.
• There are multiple types of load balancers:

o Round Robin: this is by default.
o least_conn: the one with the least client connection will be picked up.
o ip_hash: each of the client has some unique key, the first few characters of this key works as server chooser. It helps in speeding up the process.

• To provide high availability load balancers, you can plug in external load balancer also.
• Caching

o Various cache related information like path, key, validity can be configured to improve the performance.
o User data is suggested not to be cached to avoid sharing one user data with other user.

API Gateway

It is used to manage the API, also referred as translator, which includes
• combining more than 1 APIs into 1
• combining responses from more than 1 API into 1
• Providing the default data/message in case of error from any API invocation
• Security management