exp questions

To handle JWT expiration, set an expiration time when issuing the token and verify it on each request. Use refresh tokens to obtain a new JWT without requiring the user to log in again. Store refresh tokens securely and use them to request a new JWT from the server when the original token expires. Implement token rotation to enhance security.

Middleware functions in Express are functions that have access to the request, response, and the next middleware function in the application’s request-response cycle. Implement middleware by defining a function with `(req, res, next)` parameters and using `app.use(middlewareFunction)` to apply it globally or `router.use(middlewareFunction)` for specific routes. Middleware can perform tasks such as logging, authentication, or request modification.

Error handling in Express is typically done using middleware. Define an error-handling middleware function with four parameters: `err`, `req`, `res`, and `next`. Use `app.use((err, req, res, next) => { /* error handling logic */ })` to catch and handle errors. Ensure you place this middleware after all route and other middleware definitions. Handle different error types and send appropriate responses to the client.

Implement rate limiting in Express using middleware like `express-rate-limit`. Install it with `npm install express-rate-limit` and configure it to limit the number of requests from a single IP address. For example, `const limiter = rateLimit({ windowMs: 15 * 60 * 1000, max: 100 }); app.use(limiter);` limits requests to 100 per 15 minutes. This helps prevent abuse and ensure fair usage of resources.

`String.prototype.match` retrieves the matches of a string against a regular expression. It returns an array of matches or `null` if no matches are found. 

const str = 'hello 123';
const matches = str.match(/\d+/);
console.log(matches); // ['123']

`String.prototype.search` searches a string for a match against a regular expression and returns the index of the first match. If no match is found, it returns -1. 

const str = 'hello 123'; 
const index = str.search(/\d+/); 
console.log(index); // 6 

Handling JWT token storage on the client side requires careful consideration to ensure security. Common methods include storing tokens in HTTP-only cookies to prevent JavaScript access, which helps mitigate XSS (Cross-Site Scripting) attacks. Alternatively, tokens can be stored in secure storage mechanisms such as localStorage or sessionStorage, but this approach may expose tokens to XSS risks. Always ensure that tokens are transmitted over HTTPS to prevent interception and that they are managed with appropriate expiration and renewal policies.

The 'exp' claim in a JWT stands for 'expiration time' and indicates the point in time after which the token is no longer valid. This claim is represented as a Unix timestamp, specifying when the token should expire. The 'exp' claim is used to enforce token expiration and ensure that tokens are only valid for a specific duration. Once the current time exceeds the 'exp' time, the token is considered expired, and further requests with that token should be rejected to maintain security and session control.

To prevent JWT token replay attacks, implement several security measures. First, use short-lived tokens with expiration claims to limit the time a token is valid. Additionally, consider using refresh tokens to issue new access tokens and invalidate old ones. Implementing nonce values or unique identifiers within the token or request can also help detect and prevent replay attempts. Lastly, ensure that tokens are transmitted over HTTPS to prevent interception and unauthorized reuse.

An Invalid Path Variable error occurs when a path variable in a URL does not match the expected format or value. Verify that path variables are correctly formatted and correspond to the expected values in routing configurations. Implement validation to ensure that variables meet expected criteria.

An Invalid Content-Type error occurs when the Content-Type header in a request does not match the expected type, such as sending JSON data with an incorrect Content-Type. Ensure that the Content-Type header is correctly set to match the request payload and validate it on the server side to handle data appropriately.

A CTE (Common Table Expression) is a temporary result set that you can reference within a `SELECT`, `INSERT`, `UPDATE`, or `DELETE` statement. Defined using the `WITH` clause, it can simplify complex queries by breaking them into more manageable parts. For example: `WITH dept_emp AS (SELECT * FROM employees WHERE dept_id = 1) SELECT * FROM dept_emp;`.

`EXPLAIN` is a command used to analyze and understand how PostgreSQL executes a query. It provides details about the query execution plan, including which indexes are used and the estimated cost of different operations. For example, running `EXPLAIN SELECT * FROM employees WHERE id = 1;` will show you the query plan and help identify performance bottlenecks or inefficiencies in your SQL queries.

An authentication flow diagram is a visual representation of the steps and interactions involved in the authentication process. It typically illustrates how a user submits credentials, how the system validates those credentials, and how authentication responses are managed. The diagram may include components such as user login, credential verification, token issuance, and session management. By mapping out these processes, an authentication flow diagram helps in understanding, designing, and improving authentication mechanisms, ensuring clarity and consistency in authentication workflows.

I have experience with succession planning by identifying and developing high-potential employees to fill key roles in the future. This involves assessing current talent, creating development plans, and providing mentorship and training opportunities. I also work with senior leaders to ensure that there is a clear plan in place for critical positions, which helps to ensure business continuity and readiness for leadership transitions.

I have extensive experience with CRM software, having used platforms such as Salesforce and HubSpot in previous roles. I am proficient in managing customer interactions, tracking sales activities, and generating reports. My experience includes customizing CRM systems to meet business needs and using data insights to improve customer service and drive sales performance.

I manage customer expectations by clearly communicating what can be achieved and providing accurate information about services and timelines. I set realistic expectations and keep customers informed about progress or any changes. By being transparent and proactive in addressing concerns, I help ensure customers have a positive experience and feel valued.

Express.js is a fast, minimal web framework for Node.js that simplifies server creation and request handling. Example: Express allows you to define routes and middleware in a structured way. A simple Express app might handle GET requests at '/home' with app.get('/home').

Synchronous errors are caught using try-catch blocks, while asynchronous errors should be handled with `.catch()` or async error-handling middleware. For example: `app.use(async (req, res, next) => { try { await asyncFunction(); } catch (err) { next(err); } });`.