Proxies In System Design | SDE Interview

In system design, a proxy is a pattern that allows a class to provide an interface for another class, without exposing the underlying implementation. It is often used to add functionality to an existing class, such as logging, caching, or security, without modifying the original class.

A proxy class acts as an intermediary between the client and the target class. The client interacts with the proxy class, which then forwards the request to the target class. The target class performs the requested operation and returns the result to the proxy, which in turn returns the result to the client.

System Design 🔥 — Key Concepts and Terms [Interview Notes]

Types of Proxies

• Forward proxies: A forward proxy is a type of proxy that is used to forward requests from clients to the internet. It is typically used in an enterprise network to control access to the internet, provide security, or to bypass network restrictions. When a client makes a request, the request is first sent to the forward proxy, which then forwards the request to the intended server. The server responds to the proxy, which in turn forwards the response to the client.

(source: Upgaurd): An example of forward proxy

• Reverse proxies: A reverse proxy is a type of proxy that is used to forward requests from the internet to a server in a private network. It is typically used to provide security, improve performance, or to handle load balancing. When a client makes a request, the request is first sent to the reverse proxy, which then forwards the request to the intended server. The server responds to the proxy, which in turn forwards the response to the client.

(Source: Upgaurd): An example of Reverse Proxy

• Transparent proxies: A transparent proxy is a type of proxy that is used to forward requests without the client’s knowledge. It is typically used to provide caching, filtering, or to hide the identity of the client or server. When a client makes a request, the request is sent directly to the transparent proxy, which then forwards the request to the intended server. The server responds to the proxy, which in turn forwards the response to the client.

Use cases of forward, reverse, transparent proxies:

• Forward proxy is mainly used in enterprise network to provide internet access to internal network users, and to cache frequently requested resources to improve network performance.
• Reverse proxy is commonly used to handle load balancing, SSL offloading and to provide security for web servers and applications.
• Transparent proxy is mainly used in ISPs and big networks for content filtering and caching, to improve internet speed and reduce internet costs.

Advantages of Proxies

1. Load balancing: Proxies can distribute incoming traffic across multiple servers, improving the overall performance and availability of a service.
2. Caching: Proxies can cache frequently requested data, reducing the load on the origin server and improving response times for clients.
3. Security: Proxies can act as a barrier between clients and servers, providing an additional layer of security by filtering out malicious traffic and hiding the identity of the origin server.
4. Anonymity: Proxies can mask the IP address of the client, providing anonymity for the user.
5. Access control: Proxies can be used to restrict access to certain resources or services, for example, only allowing certain IP addresses to access a specific website.
6. Content Filtering: Proxies can be used to block or filter certain types of content, for example, blocking access to websites with adult content in a workplace setting.
7. Improving Speed: Proxies can also be used to improve internet speed by compressing traffic and serving cached content.

Use Cases of Proxies in General

1. Web Application Firewalls (WAFs): Proxies can be used to provide an additional layer of security for web applications by filtering out malicious traffic and protecting against common web-based attacks, such as SQL injection and cross-site scripting (XSS).
2. Content Delivery Networks (CDNs): Proxies can be used to distribute content across multiple servers in different geographic locations, improving the performance and availability of a service for users. This is done by caching frequently requested data and directing clients to the nearest server.
3. API gateways: Proxies can be used to provide a single entry point for accessing backend services, such as microservices. This allows for better control over access to these services, as well as the ability to add additional functionality, such as authentication and rate limiting.
4. Reverse Proxies: Proxies can be used to accept incoming traffic and forward it to one or more backend servers based on the URL requested. This allows for better control over access to these services, as well as the ability to add additional functionality, such as authentication and rate limiting.
5. Forward Proxies: Proxies can be used to forward client request to the internet, this allows to hide the IP of the client and to block certain type of content.
6. VPN Proxies: Proxies can be used to establish a Virtual Private Network(VPN) connection, allowing users to securely access resources on a private network from a remote location.
7. Load Balancing Proxies: Proxies can be used to distribute incoming traffic across multiple servers, improving the overall performance and availability of a service, and also allow for easy scaling when traffic increases.

Designing and implementing a proxy-based system involves several key considerations:

1. Capacity planning: It’s important to understand the expected traffic patterns and usage of the system to ensure that the proxy infrastructure can handle the load. This includes considering factors such as the number of concurrent connections, the rate of incoming requests, and the amount of data that will be transferred.
2. Failover: To ensure high availability, it’s important to design a proxy-based system with failover capabilities. This can be achieved by using multiple proxies in a load-balanced configuration and implementing a monitoring system to detect and automatically failover to a backup proxy if necessary.
3. Monitoring: To ensure the optimal performance of a proxy-based system, it’s important to implement monitoring and logging. This includes tracking key metrics such as request and response times, error rates, and traffic patterns. This data can be used to identify and troubleshoot issues, as well as to make informed decisions about scaling the infrastructure.
4. Security: Security should be considered when designing and implementing the proxy-based system, it’s important to have firewalls, intrusion detection systems and other security features in place to protect against threats such as DDoS attacks, SQL injection, and cross-site scripting.
5. Scalability: It’s important to design the system for easy scaling, this can be achieved by using load balancers and cloud-based infrastructure that allows for easy scaling of resources.
6. Performance: Performance should be considered when designing the proxy-based system, it’s important to use caching, compression and other techniques to improve the performance of the system.
7. Configuration: Proper configuration of the proxy-based system is important to ensure that it functions as intended, this includes configuring firewall rules, rate limiting, and other security features.

Load Balancing In System Design | SDE Interview

The Future of Proxies

The future of proxies is likely to involve increased use of cloud-based infrastructure and automation. As more and more companies move their services to the cloud, it’s likely that proxy-based systems will also be hosted on cloud-based infrastructure, such as Amazon Web Services (AWS), Microsoft Azure, and Google Cloud Platform (GCP). This will make it easier for companies to scale their proxy infrastructure to meet changing traffic patterns and usage.

Another trend in the future of proxies is the increased use of automation and machine learning. Proxies can be configured to automatically adjust their behavior based on real-time traffic patterns, usage, and other data. This can help to improve the performance and security of a proxy-based system, as well as to make it easier to manage.

The trend towards edge computing and the Internet of things (IoT) will also have an impact on the future of proxies. As more and more devices become connected to the internet, it’s likely that proxy-based systems will be used to manage and secure traffic at the edge of the network, where devices and sensors are located.

Another trend in the future of proxies is the increased use of encryption and secure protocols like HTTPS, this will make it more difficult for attackers to intercept or tamper with traffic.

In summary, the future of proxies is likely to involve increased use of cloud-based infrastructure and automation, as well as the use of edge computing and IoT to manage and secure traffic. Additionally, the increased use of encryption and secure protocols will further improve the security of the proxy-based systems.

Conclusion

In conclusion, proxies play an important role in system design by providing load balancing, caching, and security. They can be used in various use cases such as web application firewalls, content delivery networks, and API gateways. Designing and implementing a proxy-based system requires careful planning and consideration of factors such as capacity planning, failover, and monitoring.

Additionally, security, scalability, and performance are also important considerations. The future of proxies is likely to involve increased use of cloud-based infrastructure and automation, as well as the use of edge computing and IoT. Furthermore, the increased use of encryption and secure protocols will further improve the security of proxy-based systems.

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