A new Lambda version must receive 10% of production traffic while 90% stays on the stable version — gradual rollout with instant rollback. Which feature does this?
A.Publish a new version and update $LATEST
$LATEST is mutable and serves everything — no split.
B.Lambda alias routing configuration splitting traffic between two versions
Correct. Weighted alias routing = traffic shifting.
C.Two separate functions behind an ALB
Duplicates the function — versioning is the designed mechanism.
D.Provisioned concurrency on the new version
Provisioned concurrency pre-warms; it doesn't route traffic.
Why this answer
Alias routing (weighted aliases) shifts a percentage of invocations between versions — the built-in canary/blue-green mechanism, also what CodeDeploy uses for Lambda. $LATEST is the mutable dev version and can't split traffic.
Correct answer: B · Last reviewed 2026-11-03
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