Khalid H

- Worked on ZK rollup, covering full end to end flow, sequencer, batcher, merkle trees, storing tx data in RocksDB, calculating a new state root & how a ZK proof is generated to confirm state transition from state root s1 to s2 via building a circuit (preparing private inputs, applying constraints, generating proof) and eventually submitting this batch + proof along with relevant metadata (new state root, batch no, compressed txs) to L1 (L2 contract) via a transaction & how the verification happens inside this Rollup contract - Worked on token withdrawals / deposits from custom chain to (Ethereum + Solana) & back, where user tokens are locked / burned in source chain & there is off-chain validators bridge setup listening to such events. These validators confirm the validity of tx with their own signature & eventually an aggregate signature is prepared & submitted along with tx to bridge contract on Ethereum / Solana, which maintains the public keys of of the validators. The bridge contract verifies the signature via aggregate public key & eventually corresponding tokens are minted to user account via token contract. The same process happens in reverse if need to deposit tokens back on source chain. In case of Solana, it’s a CPI from the bridge contract to invoke the SPL token program with the `mint` authority & similarly on Ethereum it’s contract-to-contract function call for custom ERC-20 token contract (representing the wrapped version of the original token) with minter role / onlyMinter access modifier. - Ethereum blockchain parsing using Go language (goroutines & channels) - Wrote Ethereum tracker in Node.js environment to download Ethereum blockchain data into local server. This tracker involved launching multiple node.js processes to parse the data in more concurrent way. - Integrating payment gateways like Easypay, Entercash & writing code as per their specifications

- Implementation of Layer 1 Lisk protocol + SDK development based on it's specifications - Writing code + peer code reviews - Contributing to protocol specifications & suggesting improvements - Initiating discussions regarding process improvement

- Developed backend system from scratch for importing Blockchain protocols - Wrote reusable components for integrating new protocols - Importing parsed data to Google BigQuery partitioned tables - Configured fresh Digital Ocean server for production environment

- Working as a dedicated offshore resource for US clients - Direct communication (Skype chat & voice calls) with clients to analyze requirements - Leading the project with support of another colleague - Managing weekly training sessions - Presenting demo to client after each module completion - Web scrapping

- Worked on different modules of yellowzip.com - Parsing big XML files from external data engines & populating yellowzip DB. - Choosing the right XML parsing technique/strategy to parse big files, so script wouldn't crash. - Applied Yahoo optimization techniques to improve front end performance - Applied back end performance techniques on DB structure, Mysql engine & SQL queries. - Applied code optimisation techniques - Developed Ajax based admin panel using front end tools

- Developing websites as per client needs using CakePHP, Smarty, Mysql, & front end tools. - Communication with client to analyse/clarify requirements - Developing AJAX based website - Presenting demos to client after each successful module completion - Using Smarty as template engine on server side for front end AJAX requests

- Sent questions to client to clarify/understand the existing complex system - Developed some websites from scratch and they went live successfully

- Joined as intern, learnt & gained experience by working on real websites - Got job offer right after 2 months in the same company - Helped seniors & management to accomplish business tasks