What is meant by request optimization when reducing API response time from 2 seconds to 300 ms?

Optimizing requests to reduce API response time from 2 seconds to 300 ms means improving performance at the level of interacting with the database or other services to reduce delays. This can include:

• Rewriting SQL queries to reduce the number of operations and use indexes.
• Caching frequently requested data.
• Using more efficient data processing algorithms.
• Parallelizing requests or asynchronous processing.
• Minimizing the amount of data transmitted.

An example in Go, where a prepared statement and caching are used to speed up the response:

var cache = make(map[int]User)

func getUser(id int) (User, error) {
    if user, ok := cache[id]; ok {
        return user, nil // return from cache
    }
    // assume db is *sql.DB
    row := db.QueryRow("SELECT id, name FROM users WHERE id = ?", id)
    var user User
    err := row.Scan(&user.ID, &user.Name)
    if err != nil {
        return User{}, err
    }
    cache[id] = user
    return user, nil
}

Thus, optimization is a set of measures aimed at reducing request processing time and data transfer.