...

 ✅ Maintained

Deprecation Plan

Java API:

// Existing method - mark as deprecated in 4.0
@Deprecated(since = "4.0", forRemoval = true)
<VR, KO, VO> KTable<K, VR> join(
    KTable<KO, VO> other,
    Function<V, KO> foreignKeyExtractor,
    ValueJoiner<V, VO, VR> joiner);

Scala API

...

No, new API only.

Test Plan

1. Unit tests:
   - Test foreign key extraction using only value (backward compatibility)
   - Test foreign key extraction using both key and value
   - Test null handling for both key and value
   - Test with various key and value types
2. Integration tests:
   

    - End-to-end tests with actual topics and data
    - Performance comparison tests
    - Error handling and recovery scenarios

...