This sounds similar to how in C#/.NET there are (at least) 3 methods to reading XML: XmlDocument, XPathDocument, or XmlReader. The first 2 are in-memory object models that must parse the entire document to build up an object hierarchy, which you then access object-oriented representations of XML constructs like elements and attributes. The XmlReader is stream-based, where you handle tokens in the XML as they are read (forward-only.)

Any large XML document will clobber a program using the in-memory representations, and the solution is to move to XmlReader. System.Text.Json (.NET built-in parsing) has a similar token-based reader in addition to the standard (de)serialization to objects approach.