Rebuilding a company's website can be a daunting task, and the Gatsby Proof-of-Concept Playbook by Sam Bhagwat serves as a comprehensive guide to help teams navigate this process using Gatsby. The playbook emphasizes starting with a proof of concept (PoC) to test different technology stacks, likening it to building a sandwich with necessary elements and optional add-ons tailored to a company's needs. Key strategies include choosing high-traffic pages for testing, evaluating performance improvements through tools like Lighthouse, and considering user experience and conversion rates. The playbook outlines various PoC scopes, such as "lift-and-shift" or "site rebrand," and provides real-world examples of companies like Berlitz and Penn State News enhancing their websites with Gatsby. It also highlights the importance of organizational buy-in, defining success metrics upfront, assigning clear responsibilities, and building a strong business case. The playbook recommends running evaluations in parallel rather than sequentially to save time, and offers support from the Gatsby team during the PoC development process.