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Rate Limit Inbound Policy

Rate-limiting allows you to set a maximum rate of requests for your API gateway. This is useful to enforce rate limits agreed with your clients and protect your downstream services.

The Zuplo Rate-Limit allows you to limit based on different attributes of the incoming request. For example, you might set a rate limit of 10 requests per second per user, or 20 requests per second for a given IP address.

The Zuplo rate-limiter also allows you to set a custom bucket name by which to effect a rate-limit using a function.

When a client reaches a rate limit - they will receive a 429 response code.



Be sure to read about policies

"name": "my-rate-limit-inbound-policy",
"policyType": "rate-limit-inbound",
"handler": {
"export": "BasicRateLimitInboundPolicy",
"module": "$import(@zuplo/runtime)",
"options": {
"rateLimitBy": "ip",
"requestsAllowed": 2,
"timeWindowMinutes": 1
  • name the name of your policy instance. This is used as a reference in your routes.
  • policyType the identifier of the policy. This is used by the Zuplo UI. Value should be rate-limit-inbound.
  • handler/export The name of the exported type. Value should be BasicRateLimitInboundPolicy.
  • handler/module the module containing the policy. Value should be $import(@zuplo/runtime).
  • handler/options The options for this policy:
    • rateLimitBy
      The identifying element of the request that enforces distinct rate limits. For example, you can limit by `user`, `ip`, `function` or `all` - function allows you to specify a simple function to create a string identifier to create a rate-limit group
    • requestsAllowed
      The max number of requests allowed in the given time window
    • timeWindowMinutes
      The time window in which the requests are rate-limited. The count restarts after each window expires
    • identifier
      The function that returns dynamic configuration data. Used only with `rateLimitBy=function`
      • export
        used only with rateLimitBy=function. Specifies the export to load your custom bucket function, e.g. `default`, `rateLimitIdentifier`.
      • module
        Specifies the module to load your custom bucket function, in the format `$import(./modules/my-module)`

Note you can have multiple instances of rate-limiting policies to use in combination. You should apply the longest duration timeWindow first, in order to the shortest duration time window.

Using a custom function

You can create a rate-limit bucket based on any property of a request using a custom function that returns a CustomRateLimitPolicyOptions object (which provides the identifier used by the limiting system).

The CustomRateLimitPolicyOptions object can be used to override the timeWindowMinutes & requestsAllowed options.

This example would create a unique rate-limiting function based on the customerId parameter in routes (note it’s important that a policy like this is applied to a route that has a /:customerId parameter).

//module - ./modules/rate-limiter.ts

import { CustomRateLimitPolicyOptions, ZuploRequest } from "@zuplo/runtime";

export function rateLimitKey(
request: ZuploRequest
): CustomRateLimitPolicyOptions {
if (request.params.customerId === "43567890") {
// Override timeWindowMinutes & requestsAllowed
return {
key: request.params.customerId,
requestsAllowed: 100,
timeWindowMinutes: 1,
return { key: request.params.customerId };
// config - ./config/routes.json
"export": "BasicRateLimitInboundPolicy",
"module": "$import(@zuplo/runtime)",
"options": {
"rateLimitBy": "function",
"requestsAllowed": 2,
"timeWindowMinutes": 1,
"identifier": {
"module": "$import(./modules/rate-limiter)",
"export": "customRateLimit"