Phabricator
Facebook's long-standing internal suite for code reviews, bug tracking, repository browsing...etc. Essentially it is Github. It includes components like Differential (code review), Maniphest (bug tracker), Herald (change monitoring), and Phriction (wiki), also most importantly the deployment status of the diffs which is much better than any similar tools externally which connected to Github ref
Mercurial
It is essentially Git. Facebook chose Mercurial (hg) over Git to manage its massive monorepo, because back in the day ~15 years ago, Git struggled with performance at Facebook's scale (millions of commits, hundreds of GBs every day). So early-stage fb engineers forked it and leveraged its distributed versioning nature to optimize engineers' productivity ref
Scuba
A distributed in-memory analytics platform built for real-time, ad-hoc querying of log data and other streams. Accessible via its web UI or SQL-like interface for rapid debugging and trend analysis. ref
Daiquery
Daiquery is a web-based notebook tool used to query data warehouses (via Presto/Spark), Scuba, and more — with visualization support. ref
Unidash
An internal dashboard platform (like Superset or Tableau) that integrates with Daiquery. It facilitates interactive, high-level visualizations with support for programmatic dashboard creation and underlying pre-aggregation support (via RaptorX extension). ref/a>
Bento
Bento builds on Daiquery, acting as a managed Jupyter notebook environment with Python, R, and rich visualisation capabilities used by data scientists and ML engineers. ref
ZippyDB
It is a highly scalable distributed key-value datastore managed as a service. It is essentially DynamoDB on AWS. ref
Thrift
A RPC framework originally developed at Facebook back in 2007, later open-sourced under Apache. It is essentially gRPC and engineers use it to communicate between internal backend services ref
Pixelcloud
An internal tool for uploading, sharing, tagging, and commenting on mockups and screenshots without compression—widely used by designers and engineers to collaborate visually. ref
Relay
It is facebook's version of GraphQL. Powers Facebook web apps, Instagram web, Workplace, etc. Relay ensures UI → GraphQL backend is efficient at massive scale (billions of queries). ref
Flow
It is facebook's approach of using Javascript with types. A static type checker for JavaScript. It adds optional type annotations to JS, giving devs type safety without full TypeScript migration. Widely used across Facebook and Instagram frontend code. Overlaps with TypeScript in functionality, but Facebook invested heavily in Flow to scale existing codebases before TS was popular. ref