Streaming Large Financial Transaction Exports Without Breaking Your API

Large financial transaction exports can easily overwhelm traditional REST APIs. When datasets reach hundreds of thousands or even millions of records, generating export files entirely in memory becomes inefficient and sometimes unstable. Many financial platforms provide some version of an “Export transactions” feature for reconciliation, accounting, tax preparation, or compliance reporting. At small scale, this is straightforward: query the transactions, generate a file, and return it to the client. Problems start appearing when those exports grow large. This post explores a practical streaming pattern for handling those exports efficiently while keeping memory usage predictable. The architectural approach discussed here is also described in more detail in my research paper: Streaming REST APIs for Large Financial Transaction Exports from Relational Databases Why Traditional Export APIs Struggle A typical export endpoint might look something like this: @GET @Path ( "/transactions/expor