Describe a time when you had to optimize a backend service that was performing poorly. What steps did you take to analyze and resolve the issue?

LeetCode #200 - Number of Islands: Given a 2D grid of '1's (land) and '0's (water), count the number of islands. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by water. ### Input - A 2D grid represented as a list of lists. ### Output - An integer representing the number of islands. ### Example Input: [[1,1,0,0,0], [1,1,0,0,0], [0,0,1,0,0], [0,0,0,1,1]] Output: 3 ### Constraints - 0 <= grid.length, grid[i].length <= 300

Can you explain the differences between synchronous and asynchronous programming in the context of backend development? Provide examples of when you would use each.