set, _ := sandboxset.New(&sandboxset.Config{
    Pool:        myPool,
    CodeDir:     "?url=https%3A%2F%2Fgithub.com%2Fpath%2Fto%2Flambda",
    ScratchDirs: myScratchDirs,
})

ref, _ := set.GetOrCreateUnpaused()   // create or reuse a sandbox
sb := ref.Sandbox()                    // access the underlying container
// ... handle request using sb.Client() ...

if broken {
    ref.Broken = true                  // mark unhealthy before returning
}
ref.Put()                              // recycles if healthy; destroys if Broken

set.Close()                            // tear down everything

type SandboxRef struct {
	set    *sandboxSetImpl
	Broken bool
	sb    sandbox.Sandbox
	inUse bool
}

func (r *SandboxRef) Sandbox() sandbox.Sandbox    // access the container
func (r *SandboxRef) Put() error                   // return to pool (or destroy if Broken)
func (r *SandboxRef) Destroy(reason string) error  // explicitly destroy and remove

type SandboxSet interface {
    GetOrCreateUnpaused() (*SandboxRef, error)
    Close() error
}

type Config struct {
    Pool        sandbox.SandboxPool  // creates/destroys sandboxes
    Parent      SandboxSet           // optional parent set to fork from
    IsLeaf      bool                 // marks sandboxes as non-forkable
    CodeDir     string               // Lambda handler code directory
    Meta        *sandbox.SandboxMeta // runtime config (memory, packages, etc.)
    ScratchDirs *common.DirMaker     // creates a writable dir per new sandbox
}