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MINOR: improve Kafka Streams transform upgrade docs #21002

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MINOR: improve Kafka Streams transform upgrade docs
mjsax Nov 27, 2025
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mjsax Nov 27, 2025
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mjsax Nov 27, 2025
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7 changes: 5 additions & 2 deletions docs/streams/developer-guide/dsl-api.html
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Expand Up @@ -3462,10 +3462,11 @@ <h3>
<p>The Processor API now serves as a unified replacement for all these methods. It simplifies the API surface
while maintaining support for both stateless and stateful operations.</p>

<p><b>CAUTION:</b> If you are using <code>KStream.transformValues()</code> and you have the "merge repartition topics"
<p><b>CAUTION:</b> If you are using <code>KStream.transformValues()</code> or <code>KStream.flatTransformValues()</code>
and you have the "merge repartition topics"
optimization enabled, rewriting your program to <code>KStream.processValues()</code> might not be safe due to
<a href="https://issues.apache.org/jira/browse/KAFKA-19668">KAFKA-19668</a>. For this case, you should not upgrade
to Kafka Streams 4.0.0 or 4.1.0, but use Kafka Streams 4.0.1 instead, which contains a fix.
to Kafka Streams 4.0.0 or 4.1.0, but use Kafka Streams 4.0.1 or 4.1.1 instead, which contain a fix.
Note, that the fix is not enabled by default for backward compatibility reasons, and you would need to
enable the fix by setting config <code>__enable.process.processValue.fix__ = true</code> and pass it
into <code>StreamsBuilder()</code> constructor.</p>
Expand Down Expand Up @@ -3680,6 +3681,8 @@ <h5 id="replacing-slang-in-text-messages-removal">Replacing Slang in Text Messag
}
}</code></pre>
<h5 id="cumulative-discounts-for-a-loyalty-program-removal">Cumulative Discounts for a Loyalty Program</h5>
<p>Below, methods <code>applyDiscountWithTransform</code> and <code>applyDiscountWithProcess</code> show how you can
migrate from <code>transform</code> to <code>process</code>.</p>
<pre class="line-numbers"><code class="language-java">public class CumulativeDiscountsForALoyaltyProgramExample {
private static final double DISCOUNT_THRESHOLD = 100.0;
private static final String CUSTOMER_SPENDING_STORE = &quot;customer-spending-store&quot;;
Expand Down