Fission is a Kubernetes-native serverless framework (FaaS) that deploys and manages functions triggered by HTTP requests, message queues (Kafka, NATS, etc.), cron schedules, and Kubernetes events. The system is composed of multiple microservices: a router that proxies HTTP requests to function pods, an executor that manages warm-pool and per-function deployment backends, a builder that compiles function packages, a fetcher sidecar that materializes code into pods, and a storage service for archive management. All resources (Function, Environment, HTTPTrigger, Workflow, etc.) are defined as Kubernetes Custom Resource Definitions (CRDs) and reconciled by controller-runtime controllers. The architecture supports multi-tenant namespaces, canary deployments via FunctionAlias and CanaryConfig CRDs, a workflow engine with event sourcing, and a pluggable state store (memory, SQLite, Postgres) for durable queues and key-value storage. Internal service-to-service communication is authenticated via HMAC signing. Observability is built on OpenTelemetry (traces, metrics, logs) and Prometheus. The CLI tool (`fission`) provides full lifecycle management and a GitOps-friendly spec system. The codebase is RFC-driven with formal verification (TLA+ specs) for critical subsystems like the workflow event log and queue lease protocol.