In systems with high-frequency Read operations, caching the database can optimize performance by reducing the I/O operations on the database server. Cached data can be quickly retrieved from memory, reducing the load on the underlying database.

To handle asynchronous errors with async/await, you should use a try/catch block around each individual await operation. This allows you to catch and handle errors for specific asynchronous operations within the async function. Option A would catch errors for the entire function, which might not provide fine-grained error handling. Options C and D are incorrect approaches for error handling with async/await.

Object keys in JavaScript are case-sensitive. This means that keys with different letter casing (e.g., 'key' and 'Key') are considered distinct in an object. The other options do not accurately describe the behavior of object keys.

In a scenario with heavy Read and Update operations, sharding is a database design strategy where you distribute the data across multiple servers or nodes. This helps balance the load and improve Read performance. Sharding ensures data consistency by managing data distribution and replication across shards. Replication (Option 2) can improve Read performance but doesn't address balancing the load directly. Denormalization (Option 3) can help with Reads but may complicate data consistency. Indexing (Option 4) helps with Read performance but doesn't balance the load.

In JavaScript, when a function is defined inside another function, it forms a "closure." A closure allows the inner function to access the outer function's variables even after the outer function has finished executing.

The fs.createReadStream method in Node.js is particularly useful when dealing with large sized files. This method allows you to efficiently read large files in smaller chunks, which can be memory-efficient for handling large datasets.

The concat() method in JavaScript creates a new array that combines the elements of the original array and the elements passed as arguments, without modifying the original array. The other methods, such as splice(), push(), and pop(), directly modify the original array.

According to semantic versioning (SemVer), when you make backward-incompatible changes or breaking changes, you should increment the major version. In this scenario, since the behavior change affects existing users, you should update to version 2.0.0.

The best way to handle errors in an Express application when building RESTful APIs is to use try...catch blocks in route handlers. This allows you to catch errors and send appropriate HTTP responses with error details. Sending 404 Not Found for all errors is not a good practice, and letting errors crash the server is even worse. Console.log() is generally used for debugging but not for handling errors.

Using labels with break or continue in JavaScript provides more control over which part of the code to skip or execute. Labels allow you to specify which loop or block of code should be affected by break or continue statements when dealing with nested loops or complex control flow.

In Express.js, you can extract route parameters using req.params.userId. Route parameters are specified in the URL path with a colon prefix, and you can access them using req.params. The other options are not the correct way to access route parameters.

Asynchronous Programming with Closures