MongoDB Internal Architecture | The Backend Engineering Show

This episode explores the evolution of MongoDB's internal architecture, specifically focusing on its storage engines and the shift from SQL-based to NoSQL approaches. Against the backdrop of the fundamental differences between SQL and NoSQL databases—primarily the data format (tables vs. documents) and the API (SQL vs. a simpler get/set)—the podcast details MongoDB's journey. Initially using the mmapv1 storage engine, which suffered from limitations like global locking and offset-based storage, MongoDB later adopted the WiredTiger engine. More significantly, the introduction of WiredTiger brought features like compression and document-level locking, improving performance and concurrency. However, even WiredTiger had its drawbacks, leading to a two-lookup process for ID searches. Finally, the podcast highlights the introduction of Clustered Collections in MongoDB 5.3, which addresses these issues by making the ID field the clustered index, resulting in a single, faster lookup for ID-based searches. This evolution showcases the ongoing challenges and innovations in database design, particularly in balancing performance, scalability, and data structure flexibility. What this means for developers is a more efficient and adaptable database system, constantly evolving to meet the demands of modern applications.