# Storage


Name	Exists before execution	Can be created during execution	Can be read during execution	Can be written during execution	Persists across executions	Use cases	Examples
Files in the `/tmp/` folder	NO	YES	YES	YES	NO	Intermediate file operations within a single execution — writing data to disk during processing before consuming or returning it, or using libraries that require a file path rather than an in-memory object.	Generating a temporary CSV from query results and reading it back; rendering a PDF or image with a library that writes to a file path; unzipping a payload before processing its contents.
Global properties	YES	NO	YES	NO	YES	Storing read-only configuration and sensitive values that must be available across multiple functions without hardcoding them in source code — credentials, constants, and lookup tables that change infrequently.	An API key or token shared by several functions (e.g., `aws_keys`, a Twilio auth token); a JSON lookup table mapping device model codes to human-readable names; a constant threshold value (e.g., max temperature alert level) reused across different processing functions.
Local files	YES	NO	YES	NO	YES	Bundling static reference data or configuration that is known at deploy time and needs to be read (but never written) during execution — decoder logic, device configuration, or parameter files that ship alongside the function code.	A `device_config.json` with per-device-type settings; a `calibration_table.csv` with sensor offsets; separate Python/JS modules (e.g., `decoder.py`, `utils.py`) organized in a `modules/` folder and imported by the main script.
External files	YES	YES	YES	YES	YES	Persisting files that must survive across executions and be created or updated at runtime — long-lived data that is too large or dynamic to fit in Global Properties, and that multiple functions or executions may need to read or write.	A running log file that each execution appends to; a trained ML model binary uploaded once and downloaded on each inference call; a shared reference dataset (e.g., a lookup CSV) updated periodically by one function and consumed by others.

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