Limitations

Arguments and return values must be serializable

Cloudified function arguments must be serializable with JSON.stringify. Faast.js uses a custom replacer() function that allows for these types to be safely passed as arguments or return values:

Buffer
Date
undefined
Infinity
-Infinity
NaN
Int8Array
Uint8Array
Uint8ClampedArray
Int16Array
Uint16Array
Int32Array
Uint32Array
Float32Array
Float64Array
Map
Set

Faast.js will throw a FaastError if it detects a case where an argument or return value cannot be serialized without a loss of information (see CommonOptions.validateSerialization). For example, the following are not supported as cloud function arguments:

Promise arguments (however Promise return values are supported)
Functions passed as arguments or return values
Class instances
... and more. The MDN documentation contains more details about specific cases.

Size limits on arguments and return values

Arguments and return values are sent through each provider's API or through a cloud queue or notification service, each of which may have a size limit. The limits will depend on the provider and mode being used:

AWS Limits

Limits for AWS Lambda are published here. These limits manifest differently for https vs queue mode.

Local limits

In local mode, faast.js uses node's process.send() to send messages to worker processes. The IPC limits are OS-specific.