Setup

Validate data and payload limits

Catch missing or incorrectly typed values before they reach your Shopify Flow workflow. FlowRelay supports a bounded set of validation rules, not the full JSON Schema standard.

Next step Read Send your first test event.

Steps

Complete these in order.

Choose when to validate

In Endpoint setup, expand Validation rules. Before mapping checks the incoming JSON; After mapping checks the custom data object.
Declare rules

Each rule needs a path and type. Add required, nullable, enum, numeric bounds, string lengths, or list sizes where appropriate. A missing optional value is skipped; explicit null needs nullable: true.
Preview good and bad samples

Use synthetic data to verify each rule. A failed preview identifies the stage and rule without delivering an event. Review and confirm before saving.

Rule examples #

Use at most 25 rules before mapping and 25 after mapping. Numeric limits apply to number/integer, length limits to string, and item limits to array. Remote schemas, arbitrary validators, and regex constraints are unsupported.

Before mapping

[
  {
    "path": "customer.email",
    "type": "string",
    "required": true,
    "minLength": 3,
    "maxLength": 200
  },
  {
    "path": "items",
    "type": "array",
    "required": true,
    "minItems": 1,
    "maxItems": 50
  }
]

After mapping

[
  {
    "path": "total",
    "type": "number",
    "required": true,
    "minimum": 0
  },
  {
    "path": "status",
    "type": "string",
    "enum": [
      "paid",
      "pending"
    ]
  }
]

Payload budgets #

Sizes are measured on UTF-8 bytes. The final Flow budget includes field names, ordinary trigger fields, custom JSON, and escaping; it is not just the visible custom-data length.

Item	Limit
Input to custom processing	65,536 bytes
Custom data JSON	20,000 bytes
Complete serialized Flow payload	49,000 bytes
Declared top-level outputs	20
Array length / JSON depth	1,000 items / 16 levels
Input/output inspection	8,192 nodes; 100,000 cumulative inspections during evaluation
Expression execution	10,000 evaluator steps; 100 stack frames; 100 ms evaluator timeout
Generated Run code output schema / code	5,000 / 50,000 bytes

Understand a rejected event #

FLR_VALIDATION_FAILED means the input or custom output did not meet the declared rules. FLR_TRANSFORMATION_FAILED means the expression could not produce valid data. FLR_TRANSFORMATION_LIMIT means processing exceeded a bound. FLR_FLOW_PAYLOAD_TOO_LARGE means the complete trigger payload exceeded its size budget. Reduce the data or correct the configuration; nothing is silently truncated.

Preview, usage, and privacy #

Sample previews do not consume live-event quota or run actions in Shopify. Saving configuration follows the existing action-intent and execution allowances. Per-installation abuse limits apply separately. Samples are ephemeral; exports include your mapping literals and defaults, so review them before sharing. Retained delivery data follows the existing plan retention policy.

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REFERENCE