Chainlink Functions Is Serverless Compute With Oracle Guarantees. Here's the Full Request Lifecycle.

The mental model most people have is too simple "Chainlink Functions lets smart contracts call APIs." That's true the same way "Ethereum lets people send money" is true. Technically accurate, misses almost everything that makes the product interesting and almost everything that matters for security. Chainlink Functions is better understood as a decentralized serverless compute platform: arbitrary JavaScript runs across every node in a DON, each node executes independently, OCR aggregates the results, and the aggregated output gets delivered back to the consumer contract through a verified callback. The "API call" is just one of the things that JavaScript can do inside that environment. The DON consensus and the threshold-encrypted secrets model are what make it meaningfully different from a centralized API proxy. This is day 9 of the 28-day Chainlink architecture series. Today covers the full request lifecycle, every contract in the chain, how threshold encryption protects secrets without exposing them to any individual node, and the integration mistakes that come from misunderstanding how billing and callbacks actually work. The four contracts you need to understand Before tracing the full lifecycle, it helps to know exactly which contract does what. FunctionsRouter : the stable, immutable entry point for consumers. Manages subscriptions and authorized consumer contracts. Its interface doesn't change when the underlying implementation upgrades, consumer contracts call sendRequest here and only here. Also handles billing: estimates fulfillment cost at request time and finalizes it at response time. FunctionsCoordinator : the interface between the Router and the DON. Emits the OracleRequest event that DON nodes watch for. Handles fee distribution to transmitters via a fee pool. Inherits from OCR2Base , meaning the full OCR consensus machinery runs here. This contract can be upgraded independently of the Router, which is why the Router exists as a stable facade in fro