Custodial Stack
Overview

Overview

The Custodial Stack allows any non-web3 client to interact with smart contracts on any EVM chain. Such clients may include:

  • USSD
  • Telegram bots
  • Websites
  • Anything that talks HTTP

Below is a high level overview of how different components interact and make up the custodial stack:

Prerequisites

The following are required in preparation of running the custodial stack:

Minimum system requirements

  • Stable internet connection
  • Access to an Ethereum/EVM node with RPC and websockets enabled
  • Atleast 2 GB of RAM (Approximate)

Chain requirements

  • 1 Ether to setup the smart contracts
  • EVM hardfork minimal requirement: Istanbul
  • Instant finality recommended (no chance of block reorgs)

Self-hosted budget guideline

This is a guide to approximate the monthly costs of completely self-hosting the custodial stack + other components listed here on a cloud provider for a small deployment which can support upto 10k active users.

Custodial Backend Stack Server

This hosts all backend services and databases.

  • Estimate: $40 - $100 (Depending on your choosen cloud provider).
  • Recommended Specs: 16 GB RAM, 8 vCPU with atleast 50 GB SSD storage.
  • Time estimate: ~ 4 - 5 hours for complete setup using provided setup instructions in the next sections.

Blockchain RPC Server (Baremetal)

This hosts the CELO RPC node and is future proofed for 1 year. We recommend using a provider which supports storage upgrades.

  • Estimate: $120 - $250 (Depending on your choosen baremetal provider).
  • Recommended Specs: 32 GB RAM, 16 CPU with atleast 2 TB SSD storage.
  • Time estimate: ~ 1 - 2 hours for complete setup using provided instructions in the next setup.

It is possible to use 3rd party RPC providers like dRPC and Ankr or completely free public RPC nodes like Forno, however, we do not recommend this.

AfricasTalking Subscription

This is required for those who want to run the USSD service within Africa. Please refer to https://africastalking.com/pricing (opens in a new tab) for more details.

  • One-time setup costs estimate: $70 - $100 (SMS ID)
  • Monthy subscription for shared USSD code: $190
  • Time estimate: Depends on AfricasTalking, tech setup is done in the Custodial Backend Stack Server.

Varying costs depending on AU (active users). If a user were to do 1 transfer daily, it would cost:

  • USSD: 1 * 45 UGX * 3 (1 min session) = 135 UGX
  • SMS: 25 UGX * 1 * 2 (SMS sent to sender and recipient) = 100 UGX
  • ~ 235 UGX per active user daily.

CELO Gas Costs requirements

Assuming there are ~500 daily transactions and you would like to sponsor all the gas costs.

  • Estimate: < 2.5 CELO/Daily

Sarafu.Network Dapp (Web3 Only)

If you would like to run your own fork/copy of the Dapp website

This component required the tracker and indexer to be setup in the custodial stack. This component can be run on Vercel for free or on a self-hosted server.

  • Estimate: Free - $25
Reth DevnetNATS Integration