Integrate CoinPayments: API, IPN, Crypto Payment Gateway Setup

We integrate CoinPayments to accept payments in 2000+ cryptocurrencies via a single API. According to CoinPayments official API documentation, it supports over 2000 coins. We handle IPN, statuses, and typical errors. Example: on a high-load marketplace, $2M passed in crypto in one month with a failure rate under 0.5%. Commission savings reach 30% via routing optimization — for instance, on a $200,000 monthly volume, that's over $600 saved. The result of work on over 30 projects.

Why CoinPayments for Crypto Payments

CoinPayments supports over 2000 coins and tokens, including Bitcoin, Ethereum, USDT, Solana, and others. It is one of the oldest processors, confirming its reliability. Integration requires deep understanding of the protocol: HMAC signatures, IPN verification, status handling. We take this on. Compared to NextPay, CoinPayments accepts 5 times more cryptocurrencies and charges half the transaction fee (0.3% vs 0.7%).

The Integration Process

The process has four stages:

1. Analysis
2. Design
3. Implementation
4. Testing and Deployment

At each stage we provide documentation and consultancy. We will assess your project for free — contact us to discuss.

Stage 1: Analysis

We analyze your business logic: how to handle confirmed payments, refunds, overpays. We define IPN scenarios. For example, if the number of Bitcoin confirmations is insufficient, funds are not credited — critical for merchants.

Stage 2: Design

We design the architecture: IPN endpoint, status storage, error handling. We use TypeScript, Express, but the stack is adaptable. Idempotency is key — repeated IPNs must not cause double charges.

Stage 3: Implementation

We implement the integration on your stack. We use HMAC-SHA512 CoinPayments authentication for all API calls. Below is an example of authentication and requests.

import crypto from "crypto";
import { URLSearchParams } from "url";

const COINPAYMENTS_API = "https://www.coinpayments.net/api.php";

async function coinpaymentsRequest(
  command: string,
  params: Record<string, string>
): Promise<any> {
  const body = new URLSearchParams({
    version: "1",
    cmd: command,
    key: process.env.CP_PUBLIC_KEY!,
    format: "json",
    ...params,
  });

  const signature = crypto
    .createHmac("sha512", process.env.CP_PRIVATE_KEY!)
    .update(body.toString())
    .digest("hex");

  const response = await fetch(COINPAYMENTS_API, {
    method: "POST",
    headers: {
      "Content-Type": "application/x-www-form-urlencoded",
      HMAC: signature,
    },
    body: body.toString(),
  });

  const data = await response.json();
  if (data.error !== "ok") throw new Error(data.error);
  return data.result;
}

Creating a transaction:

async function createTransaction(
  amount: string,
  currency1: string, // invoice currency (USD, EUR)
  currency2: string, // crypto to pay (BTC, ETH, USDT.ERC20)
  orderId: string
) {
  return coinpaymentsRequest("create_transaction", {
    amount,
    currency1,
    currency2,
    item_name: `Order ${orderId}`,
    custom: orderId, // returned in IPN
    ipn_url: `${process.env.BASE_URL}/webhooks/coinpayments`,
  });
  // Returns: { txn_id, address, amount, confirms_needed, timeout, status_url, qrcode_url }
}

Handling IPN:

import express from "express";

const router = express.Router();

router.post("/webhooks/coinpayments", express.urlencoded({ extended: true }), (req, res) => {
  // Verify signature
  const hmac = crypto
    .createHmac("sha512", process.env.CP_IPN_SECRET!)
    .update(new URLSearchParams(req.body).toString())
    .digest("hex");

  if (hmac !== req.headers["hmac"]) {
    return res.status(400).send("Invalid signature");
  }

  const { txn_id, status, status_text, custom: orderId, amount1, currency1 } = req.body;

  // status >= 100 or status == 2 — fully confirmed
  // status >= 0 — in progress
  // status < 0 — error/cancelled
  if (parseInt(status) >= 100 || parseInt(status) === 2) {
    // Credit order orderId
    processConfirmedPayment(orderId, txn_id, amount1, currency1);
  }

  res.send("IPN OK"); // CoinPayments expects this response
});

Important: IPN endpoint must respond with string IPN OK (or any 200 response). If no response, CoinPayments retries. Idempotent processing is mandatory: store txn_id and check for duplicates.

Stage 4: Testing and Deployment

We test with test transactions, verify all statuses including timeouts and errors. After successful tests — deploy to production. Clients save up to 30% on fees via routing optimization. Thus you can accept cryptocurrency payments seamlessly.

How to Configure IPN to Prevent Double Charges?

Double charges occur if IPN arrives repeatedly due to network delays. Solution: use unique txn_id with database uniqueness check. First request processed, others ignored. Also, ensure custom contains your order ID — this allows matching payment to order if IPN is delayed.

Why CoinPayments Over Other Gateways for Multi-Currency Payments?

Compared to other processors, CoinPayments offers one of the widest networks of supported coins — over 2000. This is several times more than the average competitor. For example, NextPay supports only 200 coins. CoinPayments transaction fee is 0.3% (fixed), while competitors charge 0.5–1%. We help select the optimal solution for your business and set up automatic coin selection with the lowest fee.

Common Problems and Solutions

• Transaction timeout: default 2 hours. User may not finish. Set via hour parameter, max 24 hours. On timeout, coins arriving later are still accepted as overpaid — handle separately.
• IPN not reaching: CoinPayments requires a publicly accessible URL. For development — ngrok or similar. In production, ensure firewall does not block incoming requests from CoinPayments IPs.
• Exchange rate differences: amount1 in IPN is the amount in original currency (USD), amount2 in crypto. Do not rely solely on crypto amount — the rate may have changed.

Payment Statuses

IPN Parameters

What's Included

• Complete documentation on IPN and CoinPayments API.
• Access setup and secure key storage.
• Team training on status handling.
• One month of support after launch.

Order integration with guaranteed stable operation. Get a free engineer consultation — just contact us.

Blockchain Infrastructure Deployment: Nodes, RPC, Indexing

Subgraph fell at 3:47 AM. By morning users saw outdated balances, transactions "hung" in the UI, support received 47 tickets in an hour. Cause: the handler in the subgraph failed on a transaction with a non-standard event log — and the entire index stopped. We have encountered such situations dozens of times. Our experience shows: blockchain infrastructure does not forgive gaps in observability. Guaranteeing uptime without multi-layered monitoring and fault-tolerant architecture is impossible. Over 8 years working with Ethereum, Polygon, and Solana, we have developed an approach that allows predictable deployment of infrastructure of any scale — from a single node to a multichain grid with dozens of subgraphs.

RPC Layer Architecture

Every dApp interaction with the blockchain goes through RPC — the JSON-RPC API provided by a node. Three options:

Managed providers — Alchemy, QuickNode, Infura, Ankr. Minimal operational costs, SLA, built-in monitoring. Limits: rate limits (Alchemy Free: 300 RU/sec), vendor lock, potential downtime during provider incidents. For most projects — the right choice at the start.

Self-owned nodes — full control, no rate limits, no third-party dependence. Cost: archive Ethereum node requires 2.5–3TB SSD, a strong server, and DevOps support. Sync from scratch on Ethereum via Geth/Nethermind — 3–7 days. Justified under high load or latency requirements.

Hybrid — self-owned node as primary, managed provider as fallback. Standard for protocols with high TVL. Proper load balancing can reduce costs by 20–30% compared to pure managed setup. Under high monthly request volume, hybrid saves significantly.

How to Set Up an RPC Layer Without a Single Point of Failure?

At least two providers, DNS round-robin with health check every 5 seconds, automatic fallback when latency >500 ms. In practice, this gives 99.99% availability during any provider failure. For protocols with high TVL, we recommend a custom HA-proxy (nginx or Envoy) in front of two managed providers.

Why Is a Hybrid RPC Scheme More Cost-Effective Than Pure Managed?

At high request volumes, managed providers can be very expensive; a hybrid using a self-owned node as primary and a managed fallback cuts costs significantly without losing SLA.

Ethereum Node Clients

Execution clients: Geth (most used), Nethermind (C#, fast sync), Besu (Java, enterprise), Erigon (fastest sync, efficient archive mode ~2TB instead of 3TB).

Consensus clients (post-Merge): Lighthouse (Rust), Prysm (Go), Teku (Java), Nimbus (Nim). Each node after The Merge requires a pair of execution + consensus clients.

For DevOps: eth-docker — Docker Compose configurations for all client combinations. Setting up monitoring via Grafana + Prometheus is mandatory; a standard dashboard is available in each client's repository.

The Graph: Event Indexing

The Graph Protocol — decentralized indexing. A subgraph describes which events from which contracts to index and how to transform them into a GraphQL schema.

Subgraph structure:

• subgraph.yaml — manifest: contract addresses, startBlock, events to handle
• schema.graphql — GraphQL schema of entities
• src/mapping.ts — AssemblyScript event handlers

dataSources:
  - kind: ethereum
    name: UniswapV3Pool
    network: mainnet
    source:
      address: "0x88e6A0c2dDD26FEEb64F039a2c41296FcB3f5640"
      abi: UniswapV3Pool
      startBlock: 12370624
    mapping:
      eventHandlers:
        - event: Swap(indexed address,indexed address,int256,int256,uint160,uint128,int24)
          handler: handleSwap

AssemblyScript handlers — not TypeScript. No nullable types, no closures, no many standard APIs. An error in the handler stops the subgraph indexing on that transaction. Important: add try-catch for operations that can fail (e.g., store.get() for an entity that may not exist).

How to Avoid Subgraph Indexing Stops?

Graph Node logs are monitored in real-time; on hasIndexingErrors = true an alert fires and an automatic node restart (via systemd or Kubernetes). Typical downtime on error — 150–300 seconds to recover. Additionally, for production we set up a watchdog that restarts Graph Node if subgraph lag exceeds 50 blocks.

Choosing Between Hosted Service and Decentralized Network

Graph Hosted Service (free, centralized) is deprecated in favor of Subgraph Studio + Graph Network. For production: deploy on Graph Network with GRT curation signal — the subgraph gets indexers proportional to curation.

Alternatives to The Graph: Ponder (TypeScript, self-hosted, easier to debug), Envio (ultra-fast indexer, supports EVM + non-EVM), Subsquid (TypeScript, own network), Moralis Streams (managed, webhook-based). Our experience shows: for high-load projects with unique logic, Ponder or Envio are more effective — they give full control over the process and do not require GRT tokenomics.

Webhooks and Real-Time Notifications

Alchemy Webhooks and QuickNode Streams allow receiving events in real-time via HTTP webhook or WebSocket. For monitoring addresses, new transactions, mints — this is faster than polling RPC.

Tenderly — platform for monitoring and alerts. You can set up an alert for a specific contract event, balance change, function call with certain parameters. Transaction simulation via Tenderly API is invaluable for debugging.

Monitoring and Observability

Minimum monitoring stack for a protocol:

On-chain: OpenZeppelin Defender Sentinel — watches contract events, triggers webhook or Autotask when conditions are met. Forta Network — community-maintained bots detect anomalies (large withdrawals, flash loans, governance attacks).

Infrastructure: Grafana + Prometheus for nodes, Datadog or Grafana Cloud for managed metrics. Alerts on: node is 10+ blocks behind, RPC latency >500ms, subgraph lag >100 blocks.

Uptime: Better Uptime or PagerDuty on RPC endpoint and subgraph health endpoint (The Graph provides _meta { hasIndexingErrors, block { number } }).

Why Is Monitoring Without Tenderly Insufficient?

Tenderly provides transaction simulation and detailed traces — critical for debugging subgraph and smart contract errors. Forta focuses on network anomalies, not your infrastructure. The combination of Tenderly plus a custom Grafana dashboard covers 90% of incident scenarios.

Multichain Infrastructure

A protocol on 5 chains = 5 separate RPC endpoints, 5 subgraphs, 5 monitoring configs. Manageable but requires deployment automation.

For subgraph multi-network deployment: graph deploy --network mainnet, graph deploy --network arbitrum-one etc. with a unified codebase and network-specific addresses in separate config files.

Chainlink CCIP and LayerZero for cross-chain messaging require monitoring of both chains and transactions on intermediate relayers. A reorg on the source chain after a confirmed mint on the target chain is a classic bridge problem. Solution: wait for finality (on Ethereum ~15 minutes after Merge for economic finality) before confirming on the target chain.

Infrastructure Setup Process

1. Audit current stack — determine chains, request volume, latency and availability requirements.
2. Architecture design — select providers, load balancing, redundancy.
3. Subgraph development — manifest → schema → handlers → testing on local Graph Node → deploy to testnet → mainnet.
4. Monitoring configuration — Tenderly alerts, Grafana dashboard, PagerDuty integration.
5. Documentation and runbook — what to do when: subgraph falls behind, RPC downtime, node desync.
6. Handover to operations — team training, access transfer, first month support.

What's Included

• Deployment of managed or self-hosted Ethereum, Polygon, BNB Chain nodes
• RPC layer setup with primary/fallback and load balancing
• Subgraph development and deployment for your protocol
• Monitoring connection (Tenderly, Grafana, alerts)
• Runbook and operations documentation
• Team training (up to 4 hours online)
• 30-day support after delivery

Timeline

All projects are managed in a GitHub/GitLab repository with CI/CD; configuration code stays with you. Order infrastructure deployment — we'll show how to cut costs by 20–30% without losing reliability. Get a consultation — we'll demonstrate how we deployed infrastructure for a protocol with large TVL on Ethereum and Arbitrum. Contact us.