Daily DSA and System Design Journal - 15

The day's focus included solving a Dynamic Programming (DP) problem named "Sum of Good Subsequences". The solution used a Counter to track counts and sums of good subsequences efficiently. It leveraged the relationships between adjacent values (a-1, a, a+1) to build subsequences. The code implementation involved iterating over the input array and updating counters based on neighboring values. The time and space complexity were both O(n), demonstrating its efficiency. The key insight was utilizing localized relationships for global subsequence sum computation, highlighting efficient DP techniques. The second part introduced Content Delivery Networks (CDNs). CDNs improve website performance by caching content globally for fast delivery. They work by directing user requests to the nearest edge server. If the content is cached, it's served immediately; otherwise, it's fetched from the origin server, cached, and served. CDNs reduce latency, distribute load, and save bandwidth on origin servers. Two main types of CDNs were discussed: Push CDNs and Pull CDNs. Push CDNs manually push content while Pull CDNs automatically fetch content. The Time To Live (TTL) is crucial for controlling cache expiration. CDNs have advantages like faster delivery and global scalability, but also disadvantages like cost and potential staleness. Various CDN providers were mentioned, including Cloudflare, AWS CloudFront, Akamai, Fastly, and Google Cloud CDN. The reflection connected the DSA concept and CDN by relating local adjacency propagation to content caching; dynamic aggregation to dynamic content refresh. Both techniques aim for global efficiency. The day's takeaway emphasized the connection between local optimization and global efficiency.