Event Filtering

Route events to endpoints based on payload content using filter expressions.

Filter syntax

Filters use JSONPath-style expressions evaluated against the event payload:

{
  "filter": [
    { "field": "$.data.amount", "operator": "gte", "value": 1000 },
    { "field": "$.data.currency", "operator": "eq", "value": "USD" }
  ]
}

All conditions must match (AND logic by default). Events that don’t match are silently skipped for that endpoint.

Operators

Operator	Description	Example
`eq`	Equal	`"$.status" eq "active"`
`ne`	Not equal	`"$.type" ne "test"`
`gt`	Greater than	`"$.amount" gt 100`
`gte`	Greater or equal	`"$.amount" gte 1000`
`lt`	Less than	`"$.priority" lt 5`
`lte`	Less or equal	`"$.retry_count" lte 3`
`contains`	String contains	`"$.email" contains "@company.com"`
`startsWith`	String starts with	`"$.path" startsWith "/api/"`
`endsWith`	String ends with	`"$.file" endsWith ".pdf"`
`exists`	Field exists	`"$.metadata.tags" exists true`
`regex`	Regex match	`"$.code" regex "^[A-Z]{3}$"`

Logical combinators

For complex filtering, use and, or, and not:

{
  "filter": {
    "or": [
      { "field": "$.data.amount", "operator": "gte", "value": 10000 },
      {
        "and": [
          { "field": "$.data.currency", "operator": "eq", "value": "USD" },
          { "field": "$.data.priority", "operator": "eq", "value": "high" }
        ]
      }
    ]
  }
}

Nesting is supported up to 10 levels deep.

Example: Route high-value orders

curl -X POST https://app.mittr.io/api/v1/endpoints \
  -H "X-API-Key: mtr_your_key" \
  -H "Content-Type: application/json" \
  -d '{
    "url": "https://billing.example.com/webhooks",
    "eventTypes": ["order.created"],
    "filter": [
      { "field": "$.data.amount", "operator": "gte", "value": 10000 }
    ]
  }'

Only order.created events with data.amount >= 10000 are delivered to this endpoint.

Combined with fan-out

Filters work alongside event type subscriptions:

An event is sent with eventType: "order.created"
Mittr finds all endpoints subscribed to order.created (or order.*)
Each endpoint’s filter is evaluated against the payload
Only matching endpoints receive the delivery

This allows fine-grained routing without duplicating events.