Using static variables is recommended in servlets to avoid thread safety issues, as they are shared among all instances of the servlet and are stored in a shared memory space.

Downtime during traffic spikes suggests a possible lack of horizontal scaling, where the application fails to dynamically add more instances to handle increased load. Monitoring and alerting can help detect such issues early.

In cloud environments, Horizontal scaling refers to the automated process of adding or removing resources as needed, also known as scaling out or in.

A Load balancer distributes network or application traffic across a number of servers.

Horizontal scaling involves adding more resources to the existing servers.

Load balancing is critical in a monolithic architecture to distribute traffic evenly across servers.

Containerization aids in scaling web applications by providing enhanced portability, allowing applications to run consistently across different environments, facilitating easier scaling and deployment.

A potential downside of round-robin load balancing in a heterogeneous server environment is the uneven distribution of load, as servers may have different capacities or capabilities, leading to suboptimal performance.

A distributed cache reduces the load on the database by storing frequently accessed data, reducing the need to query the database, and thereby enhancing the scalability of a web application.

Achieving Data consistency is a common challenge when scaling stateful applications, as it involves ensuring that data is synchronized across multiple instances of the application.

'Sticky session' refers to a session that retains client affinity, meaning requests from the same client are directed to the same server, enhancing user experience in stateful applications.

The load balancing algorithm that distributes requests based on the server with the least connections is known as the Least Connections algorithm.