Amazon DocumentDB Serverless is now generally available, providing a configuration that automatically scales compute and memory based on application demand, leading to significant cost savings. It supports existing MongoDB-compatible APIs and allows for easy transitions from provisioned instances without data migration, making it ideal for variable, multi-tenant, and mixed-use workloads. Users can manage capacity effectively and only pay for what they use in terms of DocumentDB Capacity Units (DCUs).

AWS Lambda offers best practices for handling billions of asynchronous invocations, emphasizing the importance of scalability and reliability in serverless applications. The article outlines techniques such as simple queueing, consistent hashing, and shuffle-sharding to mitigate issues like noisy neighbors and traffic spikes, ensuring efficient load distribution and fault tolerance. Additionally, it highlights proactive monitoring and resilience strategies to maintain service quality during high-demand periods.