Two workers use one wallet. Stop nonce collisions and blocked sends.
Build Ethereum nonce management around a per-wallet dispatcher and durable reservations. Test competing local allocations and replacement identity in Node.js.
Blockchain Engineering
Your RPC providers disagree. Fail over without mixing chain states.
Build Ethereum RPC failover that checks network identity and pins related reads to one block. Test lagging and wrong-chain providers with Node.js.
Your transaction broadcast timed out. Did it reach the network?
Handle an Ethereum transaction broadcast timeout without creating another transfer. Persist signed attempts and reconcile their original transaction identity.
Your swap simulation passed, but execution failed. What changed?
Build DEX swap preflight checks with quote age, allowance, integer slippage bounds and receipt reconciliation. Test changing conditions in Node.js.
Your blockchain listener disconnected. Recover the events it missed.
Build blockchain event backfill around durable checkpoints, overlapping ranges and canonical hashes. Test duplicate logs and replacement blocks in Node.js.
Your app credited a deposit, then the block disappeared
Handle a blockchain deposit reorganisation with provisional credit, canonical block checks and finality-aware release. Test a local ledger model in Node.js.