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Conditionals

Starts With

Checks if a string value starts with a specified prefix.

Overview

The starts_with condition evaluates whether a field's string value begins with a specified prefix. This is useful for matching URL paths, ID prefixes, namespace patterns, and other cases where the beginning of a string is significant.

Use Cases

• URL Path Routing: Route based on URL path prefixes
• ID Namespace Matching: Match IDs with specific prefixes
• Environment Detection: Identify environments by hostname prefixes
• Log Source Routing: Route logs based on source prefixes

Configuration

Setting	Type	Required	Description
key	string	Yes	The field path to check. Supports dot notation for nested fields. Use * to check all keys.
value	string	Yes	The prefix to check for.
case_insensitive	boolean	No	If true, performs case-insensitive comparison.
not	boolean	No	If true, inverts the condition (matches if value does NOT start with prefix).

Examples

URL Path Routing

Route API requests:

Code
{
  "type_id": "starts_with",
  "config": {
    "key": "path",
    "value": "/api/v2/"
  }
}

Matches:

Code
{"path": "/api/v2/users"}
{"path": "/api/v2/orders/123"}
{"path": "/api/v2/"}

Does not match:

Code
{"path": "/api/v1/users"}
{"path": "/web/dashboard"}
{"path": "api/v2/users"}

ID Prefix Matching

Match IDs with specific prefixes:

Code
{
  "type_id": "starts_with",
  "config": {
    "key": "id",
    "value": "usr_"
  }
}

Matches:

Code
{"id": "usr_12345"}
{"id": "usr_abc"}

Does not match:

Code
{"id": "ord_12345"}
{"id": "12345"}

Case-Insensitive Prefix

Match protocols regardless of case:

Code
{
  "type_id": "starts_with",
  "config": {
    "key": "url",
    "value": "https://",
    "case_insensitive": true
  }
}

Matches:

Code
{"url": "https://example.com"}
{"url": "HTTPS://EXAMPLE.COM"}
{"url": "Https://Example.com"}

Environment Detection

Identify production hosts:

Code
{
  "type_id": "starts_with",
  "config": {
    "key": "hostname",
    "value": "prod-"
  }
}

Matches:

Code
{"hostname": "prod-web-01"}
{"hostname": "prod-api-east"}

Does not match:

Code
{"hostname": "staging-web-01"}
{"hostname": "dev-api"}

Exclusion Check

Match records that do NOT start with a prefix:

Code
{
  "type_id": "starts_with",
  "config": {
    "key": "path",
    "value": "/internal/",
    "not": true
  }
}

Matches:

Code
{"path": "/api/users"}
{"path": "/public/assets"}

Does not match:

Code
{"path": "/internal/admin"}
{"path": "/internal/metrics"}

Nested Field Check

Check prefixes in nested fields:

Code
{
  "type_id": "starts_with",
  "config": {
    "key": "request.path",
    "value": "/admin/"
  }
}

Matches:

Code
{"request": {"path": "/admin/users"}}
{"request": {"path": "/admin/settings"}}

Log Source Routing

Route logs by source prefix:

Code
{
  "type_id": "starts_with",
  "config": {
    "key": "source",
    "value": "aws."
  }
}

Matches:

Code
{"source": "aws.cloudwatch"}
{"source": "aws.s3"}
{"source": "aws.lambda"}

Common Patterns

API Version Routing

Route different API versions:

V2 API:

Code
{
  "type_id": "starts_with",
  "config": {
    "key": "path",
    "value": "/api/v2/"
  }
}

V1 API (legacy):

Code
{
  "type_id": "starts_with",
  "config": {
    "key": "path",
    "value": "/api/v1/"
  }
}

Multiple Prefix Matching

Route based on any of several prefixes:

Code
{
  "operator": "or",
  "conditions": [
    {"type_id": "starts_with", "config": {"key": "id", "value": "usr_"}},
    {"type_id": "starts_with", "config": {"key": "id", "value": "org_"}},
    {"type_id": "starts_with", "config": {"key": "id", "value": "team_"}}
  ]
}

Public vs Internal Routes

Separate public and internal traffic:

Public routes:

Code
{
  "operator": "or",
  "conditions": [
    {"type_id": "starts_with", "config": {"key": "path", "value": "/api/"}},
    {"type_id": "starts_with", "config": {"key": "path", "value": "/public/"}}
  ]
}

Internal routes:

Code
{
  "operator": "or",
  "conditions": [
    {"type_id": "starts_with", "config": {"key": "path", "value": "/internal/"}},
    {"type_id": "starts_with", "config": {"key": "path", "value": "/admin/"}}
  ]
}

Exclude Static Assets

Filter out static asset requests:

Code
{
  "operator": "and",
  "conditions": [
    {"type_id": "starts_with", "config": {"key": "path", "value": "/static/", "not": true}},
    {"type_id": "starts_with", "config": {"key": "path", "value": "/assets/", "not": true}}
  ]
}

Combined Prefix and Suffix

Match both beginning and end:

Code
{
  "operator": "and",
  "conditions": [
    {"type_id": "starts_with", "config": {"key": "filename", "value": "report_"}},
    {"type_id": "ends_with", "config": {"key": "filename", "value": ".pdf"}}
  ]
}

Matches:

Code
{"filename": "report_2024.pdf"}
{"filename": "report_quarterly.pdf"}

Service Namespace Routing

Route by service namespace:

Code
{
  "operator": "and",
  "conditions": [
    {"type_id": "starts_with", "config": {"key": "service", "value": "payment."}},
    {"type_id": "equals", "config": {"key": "environment", "value": "production"}}
  ]
}

Best Practices

1. Include delimiters: Include trailing slashes or dots (e.g., /api/ not /api) to avoid partial matches.

2. Use case_insensitive for URLs: URLs may have inconsistent casing.

3. Combine with ends_with: For matching both prefix and suffix patterns.

4. Consider URL encoding: URL paths may contain encoded characters.

5. Be specific: Longer prefixes are more precise and reduce false matches.

Type Handling

• Strings: Direct prefix comparison
• Numbers: Converted to strings first (e.g., 123 starts with "1")
• Booleans: Converted to "true" or "false" strings
• Arrays/Objects: Not supported for direct comparison
• Missing fields: Returns false (or true if not is set)

Limitations

• Simple prefix matching only (no patterns or wildcards)
• Single prefix per condition (use or for multiple prefixes)
• No support for matching multiple prefixes in one condition

Troubleshooting

Not matching expected values:

• Check for leading whitespace or special characters
• Verify case sensitivity settings
• Ensure the full prefix is specified

Unexpected matches:

• The prefix might be too short
• Add delimiters to make prefix more specific

Case sensitivity issues:

• Enable case_insensitive for user-generated content
• URLs and paths may have mixed casing