Harsh Kumar Rai

Protocol engineer | Solana & Rust
PDAs, CPI, native + Anchor programs
Background: Solidity & Found
Open to Web3 / protocol roles

[Harsh Kumar Rai @HarshKumar99283]

Built a real time matching engine in Rust
It supports limit orders, partial fills, price time priority, WebSocket updates, and a live candlestick chart deployed with Rust backend (Railway) + React frontend (Vercel).
Experiment tip: try alternating aggressive buy and sell orders at different price levels to see real volatility and candle formation Next step → pushing parts of this into Solana smart contracts. Open to collaboration if anyone wants to build

deploy link : https://t.co/6s4tLtwFsO
codebase : https://t.co/CezJqw4nHJ

@100xDevs @kirat_tw

[Harsh Kumar Rai @HarshKumar99283]

Building my real time matching engine on Rust made me appreciate ownership + borrow rules.

When you are mutating orderbook state under concurrency, safety actually matters.

Now I understand why serious infra teams use Rust.

[Harsh Kumar Rai @HarshKumar99283]

@cipherweb3_ hi , i am good in rust, solana and solidity , you can some of my projects i posted on my profile like rust orderbook in trading

[Harsh Kumar Rai @HarshKumar99283]

i am keeping a public repo of Solana protocol learning
native programs
Anchor programs
PDAs & CPI

Not demos. Learning tools.
Only projects and code
https://t.co/RE8h5Bg6QI

[Harsh Kumar Rai @HarshKumar99283]

Wrote the same Solana logic with and without Anchor.
Native Solana forces you to think about:
account ownership
mutability
rent & serialization
Anchor speeds you up, but hides important constraints.
Both matter.
• Fixed a 1GB git history mistake (never commit target/ 💀)
Building in public.
🔗 https://t.co/MpR7Os8J9N

[Harsh Kumar Rai @HarshKumar99283]

@0xaniketsharma @rathfinance Interested. I have been building protocol level smart contracts (merkel vesting,staking, vesting, crowdfunding) using Solidity and Foundry with proof of work in x

my work https://t.co/EvnnmcczB4
my resume : https://t.co/aAoLy8PSSt

[Harsh Kumar Rai @HarshKumar99283]

One subtle part of staking protocols is reward settlement order.

Rewards must always be settled before modifying stake balances.

Otherwise users can lose rewards or gain unfair advantage.

This project reinforced why CEI + ordering matters more than most people think.

#SmartContracts #Security

[Harsh Kumar Rai @HarshKumar99283]

Built an ERC20 staking protocol using index based (Aave style) reward accounting.
Instead of updating rewards per user, rewards accrue globally and users settle lazily on interaction.
Result:
• O(1) gas per action
• Fair, time weighted rewards
• No loops
Written in Solidity, tested with Foundry.
Repo: https://t.co/yleHBXqPQt
#Solidity #DeFi #Web3 @kirat_tw @100xDevs

[Harsh Kumar Rai @HarshKumar99283]

Design choice in my Merkle Vesting project:
Used a global vesting schedule instead of per-user schedules.
Why?
• lower gas
• simpler invariants
• easier to audit
Most real airdrops don’t need per user schedules.
#Solidity

[Harsh Kumar Rai @HarshKumar99283]

Wrapped up my ERC20 Merkle Vesting contract.
Key focus areas:
• Merkle proof based allocation
• Cliff + linear vesting correctness
• Defensive Foundry tests for edge cases
Moving on to a staking protocol next.
codebase of project: https://t.co/7JB4vP1cGr
#Solidity #Foundry #Web3 @100xDevs @kirat_tw

[Harsh Kumar Rai @HarshKumar99283]

This pattern (checks + effects + interactions) shows up everywhere in
financial smart contracts. Easy to miss without tests.

[Harsh Kumar Rai @HarshKumar99283]

Found a small but important issue in vesting logic today.
Problem:
released amount not updated before transfer
Fix:
update state before external call + regression test
Security is mostly about ordering.
#Solidity #Web3

[Harsh Kumar Rai @HarshKumar99283]

Finished Foundry tests for core ERC20 vesting contract.

Covered cliff enforcement, linear vesting, and doublerelease protection.
Next up: Merkle proof based airdrop integration.

Testing time based logic is nonnegotiable.
codebase of project : https://t.co/7JB4vP1cGr
#Solidity #Foundry @100xDevs @kirat_tw

[Harsh Kumar Rai @HarshKumar99283]

Hi today i will be tarting my ERC20 Vesting + Merkle Airdrop project.
Focus:
• cliff + linear vesting
• Merkle proof-based allocation
• Foundry tests for time-based edge cases

Goal is production level correctness and functionality
#Solidity #Foundry

[Harsh Kumar Rai @HarshKumar99283]

Built an Upgradeable ERC20 Vesting Vault (UUPS) in Solidity. @100xDevs @kirat_tw
What I built
ERC20 vesting with cliff + linear unlocks
UUPS proxy pattern (ERC1967)
Owner-controlled upgrades using upgradeTo
Successfully upgraded logic V1 → V2 on Sepolia
State preserved after upgrade
Code: https://t.co/m8YpcKCwJN
#Ethereum #Solidity #Web3 #SmartContracts

[Harsh Kumar Rai @HarshKumar99283]

@WakeFramework @100xDevs @kirat_tw Thanks a lot
Foundry definitely helped me gain confidence with testing, and wagmi v2 + viem felt much cleaner than older stacks.
Will explore Wake more deeply for real time security feedback

[Harsh Kumar Rai @HarshKumar99283]

Day 29 Ethereum solidity project #2
@100xDevs @kirat_tw
Just deployed a Web3 Crowdfunding dApp
Built with:
Solidity + Foundry
React + Vite
wagmi v2 + viem
Deployed on Vercel
Learned a LOT about wagmi v2 ,smart contracts etc
Deploy link: https://t.co/D4xP8LXKHx
github codebase: https://t.co/iDOw8fnSvH