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Building Subscription Services with SWIG

SWIG’s token limit feature provides a powerful way to implement subscription-based services on Solana. This guide demonstrates how to create a subscription service that charges users monthly using SWIG’s token limit capabilities. You can find the complete example code here:
Examples with svm in the file name use LiteSVM for testing. Those without svm in the file name use a local validator. Which you can run with the bun start-validator command.

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Overview

In this example, we’ll create a subscription service that:
  • Charges users $10 USDC monthly
  • Uses SWIG’s token limit feature to enforce the subscription amount and period
  • Demonstrates how the limit resets after the specified period

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Key Concepts

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Token Limits

SWIG’s token limit feature allows you to:
  • Set a maximum amount of tokens that can be transferred within a specified block period
  • Automatically reset the limit after the period expires
  • Track limits per token mint (supporting multiple tokens)

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Block Period

In this example, we use a block period of 216,000 blocks, which approximates one month given Solana’s average block time of 400ms: 
// 400ms per block
// 1 month ≈ 30 days * 24 hours * 60 minutes * 60 seconds * (1/0.4) blocks/second
// ≈ 216,000 blocks

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Implementation

The example demonstrates:
  1. Creating a SWIG wallet with root authority
  2. Setting up a subscription service authority with token limits
  3. Processing subscription paymentsI
  4. Handling period resets
Here’s a key snippet showing how to set up the subscription authority:
  • Classic
  • Kit
// Set subscription service authority with 0.1 SOL monthly limit
// 400ms per block, so ~216000 blocks per month
const subscriptionActions = Actions.set()
  .solRecurringLimit({
    recurringAmount: BigInt(0.1 * LAMPORTS_PER_SOL), // 0.1 SOL
    window: BigInt(216000),
  })
  .get();

const addSubscriptionAuthorityIx = await getAddAuthorityInstructions(
  swig,
  rootRole.id,
  createEd25519AuthorityInfo(subscriptionServiceKeypair.publicKey),
  subscriptionActions,
  { payer: rootKeypair.publicKey },
);

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Use Cases

This pattern enables various subscription-based services:
  1. SaaS Applications
    • Monthly software subscriptions
    • Tiered service plans
    • Usage-based billing
  2. Content Platforms
    • Premium content access
    • Streaming services
    • Digital publication subscriptions
  3. Gaming Services
    • Monthly game passes
    • Premium features access
    • In-game subscription benefits
  4. DeFi Services
    • Trading fee subscriptions
    • Premium analytics access
    • Automated trading services

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Complete Example

For a complete working example that includes both client and server implementations, check out the SWIG SDK Example Repository. This repository demonstrates:
  • Frontend subscription management
  • Backend subscription processing
  • Error handling and edge cases
  • User management integration

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Best Practices

  1. Error Handling
    • Always verify transaction success
    • Handle failed payments gracefully
    • Implement retry mechanisms
  2. User Experience
    • Notify users before renewal
    • Provide clear subscription status
    • Implement grace periods
  3. Security
    • Secure key management
    • Rate limiting
    • Transaction monitoring
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