Michael C.

MAS-licensed payment institution (fiat + stablecoin). Owned the core flow of the consumer e-wallet app: top-up → withdrawal → daily reconciliation; every balance change is booked by the wallet service.

• –Concurrency safety (no overdraft): a single conditional UPDATE checks and deducts the balance under a row lock, so concurrent debits queue up and never go negative.
• –Idempotent APIs: one-time Redis tokens block duplicate submits; a unique index on the business order ID is the final guard.
• –Lost-callback recovery: verify signature and amount on channel callbacks; scheduled jobs query the channel to recover missed notifications.
• –Idempotent payouts: freeze funds before payout; on channel timeout only query, never resend; deduct on success, unfreeze on failure.
• –Eventual consistency: debit and pending notification are written in one DB transaction, then delivered via Kafka with retries (local message table).

Huobi Wallet: a non-custodial multi-chain wallet with ~12M users (private keys stay on the user's phone). Owned the core flow: wallet creation → on-chain transfer → deposit detection → deposit notification.

• –Chain reorgs: detect broken parentHash links, roll back and rescan; credit deposits only after enough confirmations.
• –OOM fix: the block scanner crashed while catching up; root-caused an unbounded queue holding blocks in memory and switched to a bounded queue with back-pressure.
• –Reliable delivery + idempotent consumption with Kafka: persist notifications before sending; each deposit is pushed exactly once.
• –Address filtering with a Bloom filter: discard non-user addresses in each block before hitting the database.
• –Scanner HA with a Redis distributed lock: one active scanner, automatic failover, resume from the saved cursor.

Ride-hailing platform. Tech lead of the company-wide search service.

• –Built the search service from 0 to 1 on Elasticsearch; weekly traffic grew from 60K to 100K.
• –Built SQL lineage parsing that automatically extracts upstream/downstream table dependencies, exposed as a query service.
• –Provided unified query APIs consumed by systems across the company.

Alibaba Group. Core developer of the scheduling system behind Alibaba Cloud DataWorks: master election, job sharding and timed triggers.

• –Master HA: nodes compete for a database row lock (SELECT … FOR UPDATE); when the master dies the lock is released and another node takes over automatically.
• –Job sharding: machines map to a fixed set of logical nodes, so scaling in/out only changes the mapping (similar to consistent hashing).
• –Quartz-based scheduling of 1M+ hourly/daily/weekly/monthly jobs; average job development time dropped from 36h to 17.45h after launch.

Mobile game company listed on the Shenzhen ChiNext board. Built the shared server side used by multiple games: log collection SDK and operations admin.

• –Designed and built a server-side game log collection SDK adopted by multiple mobile games.
• –Developed and maintained the Java operations admin system and its scheduled jobs.