API functions

API functions are user-defined TypeScript functions that handle web requests. You can use them to customize the API layer of your app with complex SQL queries, authentication, data from external sources, and more.

API functions are built on top of Hono, a fast and lightweight routing framework.

Example projects

These example apps demonstrate how to use API functions.

• Basic - An ERC20 app that responds to GET requests and uses Drizzle to build custom SQL queries.
• tRPC - An app that creates a tRPC server and a script that uses a tRPC client with end-to-end type safety.

Get started

import { ponder } from "ponder:registry";
 
ponder.get("/hello", (c) => {
  return c.text("Hello, world!");
});

Hello, world!

import { ponder } from "ponder:registry";
import { graphql } from "ponder";
 
ponder.use("/", graphql());
ponder.use("/graphql", graphql());
 
// ...

Query the database

The API function context includes a ready-to-use Drizzle database client at c.db. To query the database, import table objects from ponder.schema.ts and pass them to c.db.select() or use relational queries.

Select

Here's a simple query using the Drizzle select query builder.

import { accounts } from "ponder:schema";
import { ponder } from "ponder:registry";
 
ponder.get("/account/:address", async (c) => {
  const address = c.req.param("address");
 
  const account = await c.db
    .select()
    .from(accounts)
    .where(eq(accounts.address, address))
    .limit(1);
 
  return c.json(account);
});

To build more complex queries, use join, groupBy, where, orderBy, limit, and other methods. Drizzle's filter & conditional operators (like eq, gte, and or) are re-exported by ponder. Visit the Drizzle documentation for more details.

Relational queries

Drizzle's relational query builder (AKA Drizzle Queries) offers a great developer experience for complex queries. The c.db.query object exposes the raw Drizzle relational query builder.

Here's an example that uses the relational query builder in an API function to find the 10 largest trades in the past hour joined with the account that made the trade. Visit the Drizzle Queries documentation for more details.

import { accounts, tradeEvents } from "ponder:schema";
import { eq, and, gte, inArray, sql } from "drizzle-orm";
 
ponder.get("/hot-trades", async (c) => {
  const trades = await c.db.query.tradeEvents.findMany({
    where: (table, { gt, gte, and }) =>
      and(
        gt(table.amount, 1_000n),
        gte(table.timestamp, Date.now() - 1000 * 60 * 60)
      ),
    limit: 10,
    with: { account: true },
  });
 
  return c.json(trades);
});

API reference

get()

Use ponder.get() to handle HTTP GET requests. The c context object contains the request, response helpers, and the database connection.

import { accounts } from "ponder:schema";
import { ponder } from "ponder:registry";
import { eq } from "ponder";
 
ponder.get("/account/:address", async (c) => {
  const address = c.req.param("address");
 
  const account = await c.db
    .select()
    .from(accounts)
    .where(eq(accounts.address, address))
    .first();
 
  if (account) {
    return c.json(account);
  } else {
    return c.status(404).json({ error: "Account not found" });
  }
});

post()

Use ponder.post() to handle HTTP POST requests.

In this example, we calculate the volume of transfers for each recipient within a given time range. The fromTimestamp and toTimestamp parameters are passed in the request body.

import { and, gte, sum } from "ponder";
import { ponder } from "ponder:registry";
import { transferEvents } from "ponder:schema";
 
ponder.post("/volume", async (c) => {
  const body = await c.req.json();
  const { fromTimestamp, toTimestamp } = body;
 
  const volumeChartData = await c.db
    .select({
      to: transferEvents.toId,
      volume: sum(transferEvents.amount),
    })
    .from(transferEvents)
    .groupBy(transferEvents.toId)
    .where(
      and(
        gte(transferEvents.timestamp, fromTimestamp),
        lte(transferEvents.timestamp, toTimestamp)
      )
    )
    .limit(1);
 
  return c.json(volumeChartData);
});

use()

Use ponder.use(...) to add middleware to your API functions. Middleware functions can modify the request and response objects, add logs, authenticate requests, and more. Read more about Hono middleware.

import { ponder } from "ponder:registry";
 
ponder.use((c, next) => {
  console.log("Request received:", c.req.url);
  return next();
});

hono

Use ponder.hono to access the underlying Hono instance.

import { ponder } from "ponder:registry";
 
ponder.hono.notFound((c) => {
  return c.text("Custom 404 Message", 404);
});
 
// ...

Reserved routes

If you register API functions that conflict with these internal routes, the build will fail.

• /health: Returns a 200 status code immediately after the app starts running. Read more about healthchecks.
• /ready: Returns a 200 status code after the app has completed the historical backfill and is available to serve traffic. Read more about heatlthchecks.
• /metrics: Returns Prometheus metrics. Read more about metrics.
• /status: Returns indexing status object. Read more about indexing status.