Github The express starter kit leverages the Oneloop nodejs SDK, but provides a helpful middleware that can be used for verifying API keys. You can fork the starter kit repo, or copy the middleware from it.

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Installation

npm install @oneloop-hq/oneloop-ts
To learn more about the this SDK, you can visit the NodeJS SDK documentation.

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Usage

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Middleware

Let’s first add the middleware that will be used to verify the API key. This will save you from having to write the same code in every route.
middleware.ts
import { OneloopClient } from "@oneloop-hq/oneloop-ts";
import dotenv from "dotenv";
import { Request, Response } from "express";

dotenv.config();

const oneloopClient = new OneloopClient({
  token: process.env.ONELOOP_KEY ?? "",
});

export const oneloopMiddleware = (config?: {
  scopes?: {
    id: string;
    read?: boolean;
    create?: boolean;
    update?: boolean;
    del?: boolean;
  }[];
  usage?: {
    id?: string;
    value: number;
  };
}) => {
  return async (req: Request, res: Response, next: () => any) => {
    try {
      let originalPattern = req.route?.path as string | undefined;
      console.log("originalPattern", originalPattern);
      if (!originalPattern) {
        originalPattern = req.app._router.stack.find((layer: any) => {
          if (layer.route) {
            return layer.route.path === req.path;
          }
          return false;
        })?.route?.path;
      }

      const isValidKey = await oneloopClient.verifyApiKey({
        key: req.headers.authorization?.replace("Bearer ", "") ?? "",
        requestedScopes:
          config?.scopes?.map((scope) => {
            return {
              id: scope.id,
              representation: scope.id,
              read: scope.read ?? false,
              create: scope.create ?? false,
              update: scope.update ?? false,
              del: scope.del ?? false,
            };
          }) ?? [],
        billing: config?.usage
          ? {
              usage: config.usage.value,
              useCustomerIdForBilling: config.usage.id ? false : true,
              id: config.usage.id,
            }
          : undefined,
        route: originalPattern,
      });

      if (isValidKey && isValidKey.status === "VALID") {
        next();
      } else {
        res.status(401).send(`Unauthorized: ${isValidKey.status}`);
      }
    } catch (error) {
      console.error(error);
      res.status(500).send(`Internal server error: ${error}`);
    }
  };
};

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Authenticate the API key

Now, let’s use the middleware in a Express route and authenticate the API key. 
// Install the middleware on the express app
app.post("/profile", oneloopMiddleware(), handler);

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Checking for permissions

You can also check for permissions in your routes. Let’s say you have a route that requires a specific read access for profile data. You want to check if the API key has the required scope before returning the data. You can pass that scope to the middleware. Let’s modify the above route to check for billing read access. 
app.get(
  "/billing",
  oneloopMiddleware({ scopes: [{ id: "billing", read: true }] }),
  getBillingInfo
);

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Add usage to your API key

You can add usage to your API key by passing the usage parameter to the middleware. This will allow you to track how much of your API is being used. Usage object takes in value and id (optional). If id is not passed, the usage will be tracked per customer based on the customerId in the API key. In the example below, we are passing in customer_123----fine_tune as the id. In this case we have built a custom meter for tracking the usage of fine-tuning a model for a customer by creating a hash of the customerId and the meter name. 
app.post(
  "/fine-tune",
  oneloopMiddleware({ usage: { value: 3, id: "customer_123----fine_tune" } }),
  fineTuneModel
);

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Retrieving usage

You can retrieve the usage of your API key by using Oneloop typescript SDK. Here’s an example of how you can retrieve the usage of an API key. This will return the usage for the meterId that was passed in on a daily basis. 
const oneloopClient = new OneloopClient({
  token: process.env.ONELOOP_KEY ?? "",
});
const meter = await oneloopClient.getBillingUsage("customer_123----fine_tune");
res.send("Meter: " + meter + " Value: " + JSON.stringify(meter));