FDSE stands for Forward Deployed Software Engineer, Palantir’s name for the engineer who builds against a customer’s data and systems. Palantir pairs the role with a Deployment Strategist who owns problem framing and stakeholders; elsewhere in the industry one person usually does both halves under the title FDE.
Worked example: on a single engagement the Deployment Strategist establishes that the client’s real bottleneck is reconciling two systems, and the FDSE builds the pipeline, the interface and the tests that do it. Gotcha: the two roles have different interview loops — the FDSE loop includes real coding rounds, the strategist loop leans on case work — so applying to the one whose interview looks easier is a good way to end up in the wrong career.