AWS bill line item
Lambda-GB-Second
The memory-allocated × duration charge for Lambda execution, metered in GB-seconds from invocation (including cold start) to return; the x86 line and the separate, cheaper Graviton/ARM line (Lambda-GB-Second-ARM) tier and bill independently.
Lambda compute duration (GB-seconds)
Verified against official AWS documentation last checked
Why it shows up
Confusing because the number isn't invocation count or wall-clock time alone. Doubling a function's memory setting doubles its GB-second rate even if duration is unchanged, so bumping memory to speed up a function can raise this line even with flat invocation counts.
x86 and ARM usage tier and bill completely independently, so migrating half your functions to arm64 doesn't just capture the per-GB-second discount. It also restarts that workload's progress toward Lambda's monthly volume pricing tiers on the x86 side.
How to cut it
- Migrate eligible functions to arm64 (Graviton) for the automatic lower GB-second rate.
- Tune memory allocation with a power-tuning tool rather than guessing. More memory can speed up CPU-bound code, but it isn't free.
- Trim cold-start-heavy dependencies and package size, since init time before the handler returns is billed too.
- Set tight function timeouts so a hung invocation doesn't run (and get billed) far longer than intended.
How to read a usage type
Lambda-GB-Second carries no region or direction token, so there's nothing to break down here.
Source
Source: AWS docs →Found Lambda-GB-Second on your own bill?
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