In the continuation of a technical series on web app security for full-stack developers, this article emphasizes the importance of server-level security for both front-end and back-end development. It discusses the critical role of choosing a reliable and secure web server, balancing the need for speed and security. Key security practices include implementing HTTPS through Strict Transport Security (HSTS) to prevent attacks like cookie theft and man-in-the-middle, using the X-XSS-Protection header to guard against cross-site scripting (XSS) attacks, and protecting against clickjacking with X-Frame-Options. The article also covers Content Security Policies (CSP) to control which content is executable on the web app, and warns about the potential downsides of aggressive caching of sensitive data, recommending the use of Cache-Control headers to mitigate risks. The author concludes by noting the importance of staying updated on server and language vulnerabilities and teases the next article focusing on user authentication and authorization.