Rust / MEV Closer: Wire Existing Monorepo to Private Flashbots Bundles & GCP KMS (5-7-Day Sprint)

We are seeking an experienced Rust Systems / Web3 Infrastructure Engineer to finalize the transaction-broadcasting boundaries of an existing multi-chain EVM Flashloan Engine monorepo.Current Platform State:The repository utilizes a strict Four-Plane Architecture (Execution, Data, Quant, Platform). The heavy lifting is 100% finished: our data ingestion plane, multi-provider ranking layers (rpc-manager), cross-DEX/triangular heuristic scanners (opportunity-engine), and full Foundry stack (Vault, DeFi Smart Accounts, Risk Manager) are fully operational. The code currently runs in an off-market simulation posture (EXECUTION_MODE=shadow) on an independent Ubuntu host.The core mathematical libraries and detectors are fully complete, but the final transaction broadcasting edge is scaffolded. This is a plug-and-play bridging task. You are not building anything from scratch; you are closing an existing code loop based on an itemized technical manual.Scope of Work (Strict 7-Day Target):Signer Hardening: Open services/signer-service. Completely remove the temporary createMockKms() process memory placeholder loop. Programmatically wire the signer loop natively to our live GCP Cloud KMS (Google Cloud Key Management Service) module using asymmetric ECDSA secp256k1 keys.Close the Broadcast Scaffold: Open services/submission-engine. Replace the non-functional software placeholder that prints static text JSON logs to the console. Write the live asynchronous network broadcast routines to transmit signed payloads directly through our provider pools.Mempool Protection: Integrate native Flashbots Relay / Builder API bundle structures straight into our transaction submission workspace. Configure off-market transaction parameters to ensure our execution calldata completely bypasses public memory pools under an "all-or-nothing" execution framework to completely block frontrunning.Canary Verification: Configure environment parameters to transition smoothly to EXECUTION_MODE=canary to run controlled, low-size live trials behind our on-chain risk gates (restricting automated initial trade sizes to a defensive 2% size limit).Required Technical Stack:Expert proficiency with Rust (tokio async runtime, ethers-rs or alloy-rs libraries).Deep operational understanding of EVM transaction execution mechanics, block-space constraints, and Flashbots / private builder relays.Basic familiarity with JavaScript/Node.js (for the signer-service KMS update) and Solidity/Foundry code structures.Budget & Milestones (Fixed-Price Escrow):Total Budget is €500 (or equivalent USD fixed fee), broken down into strict verifiable milestones: Milestone 1 (€100): Signer Hardening (GCP Cloud KMS module integration & mock loop removal complete). Milestone 2 (€150): Submission Engine closure (Local sandbox testnet network broadcast functioning). Milestone 3 (€250): Flashbots bundle routing integration complete and Canary environment verification active .You will be working directly with our internal Code Auditor / Quality Assurance lead, who will run independent sanity checks on your code commits locally on an Anvil fork network before any escrow milestone capital is released.Please apply with examples of your previous Rust execution architecture history, private bundle integration scripts, or your active GitHub developer profile handle. Looking to onboard and initialize this sprint immediately.