01
Function-Based Compute
Handing off capacity management: the latency and retry difference across synchronous, asynchronous, and stream-based invocation models, where cold start comes from and what mitigating it costs, the design constraint of memory, duration, and concurrency thresholds, gradual release through versioning and aliases, package size management with shared layers, and why serverless does not fit long-running, state-heavy jobs.
- 01 The Serverless Concept The same day's workload is run in two arrangements: the always-on instance and the function invoked on demand; idle capacity, requests served at peak, and the hour the night job finishes are counted side by side, the base load is scanned from zero to sixty-five thousand to work out the break-even load level, and the ten handed-off decisions with the eight numbered constraints that come back in return are gathered into a single ledger.
- 02 Function Invocation Models The same validation job is run through three invocation models and four things are counted separately: the latency the caller sees, who sees the error, who owns the retry, and the rate of repeated processing; batch read size is then scanned from one to two thousand five hundred in the stream-based model to work out call count, extra processing, the healthy records dragged into the dead letter queue, and the batch that no longer fits the duration limit.
- 03 Cold Start A warm pool model is run to count whether a request finds an instance: in three fictional traffic profiles, the cold call rate, the duration added to latency, and the requests that land in the queue are measured; pool lifetime is scanned from zero to eighteen hundred seconds to work out the threshold where the cold rate drops and the idle instance-seconds that come back in return, and three mitigation paths are priced separately.
- 04 Resource and Duration Limits Three thresholds — memory, duration, and concurrency — are applied to a set of twelve jobs, and how many jobs do not fit is counted; scanning memory tiers shows duration dropping while unit cost draws a valley, with the cheapest point landing in the middle; when the concurrency limit is shared at the account level, one function starving another is measured with the throttle rate and the lost requests.
- 05 Versioning and Aliases Weight shifting through the alias is measured: the version stays unchanged, the alias moves. At every step, the affected requests and the round where the difference disappears are counted; cold start's interference with the canary measurement and rollback being a single key turn are worked out separately.
- 06 Shared Layers and Dependencies The relationship between package size and cold start is scanned: when dependencies move to a shared layer, the package shrinks but the bytes pulled do not change. Version pinning's storage cost, a layer update's radius, and an unused dependency's cost in bytes moved are counted.
- 07 Cases Where Serverless Is Not Suitable Five job types are compared on the axes of duration, state, and cost: for each type the item that exceeds the threshold is written by name, and the cost of splitting an unfit job to make it fit is counted as steps, interim state, and failure points. The topic closes with a table showing which job fits serverless, which does not, and why.