Objective 1.2
PDEDesigning for reliability and fidelity
Objective 1.2 sits in Designing data processing systems, which carries 22% of the Data Engineer exam. The questions below are original, written from the official objective title above, and each explanation cites the Google Cloud page it rests on.
Objective title verbatim from the official objectives. Google Cloud exam page ↗
A worked example
Shown solved, with the whole explanation open: this is what every question here carries.
A team runs one Dataflow pipeline in batch and another in streaming, and neither job sets a processing mode explicitly. Which guarantee applies to each job?
Correct.
Concept
A processing guarantee is a property of the runner's defaults, and a pipeline that never states a mode still has one. Assuming otherwise leads to sinks built for the wrong contract.
Why A
Batch pipelines always use exactly-once processing. Streaming pipelines use exactly-once by default and can opt into at-least-once instead.
Source
Google Cloud: Exactly-once in Dataflow, checked August 2026Batch pipelines always use exactly-once processing. Streaming pipelines use exactly-once processing by default, but can also use at-least-once processing .
Now you: objective 1.2 questions
No account needed. The explanation opens when you answer.
Sample question 1 of 3
An engineer runs a streaming pipeline that counts events per time window and finds a few events missing from the totals. What does exactly-once processing not promise here?
Sample question 2 of 3
A transform in a Dataflow streaming job calls an external payment API for each record, and the job uses exactly-once processing. What should the team expect from that call?
Sample question 3 of 3
An engineer reads Dataflow worker logs and sees the same record processed three separate times. What can be concluded about what was committed?
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Read the sources
These are the official pages the questions above cite. Reading them is studying the objective from the primary source, which is what the explanations point you toward anyway.