What this PR does / why we need it:

Adds comprehensive blog post documenting Feast's unified transformation framework, covering the Transformation API, multiple compute engines, and migration patterns.

Changes

Blog Post (infra/website/docs/blog/transformation-framework.md)

• Documents unified Transformation API with 6 execution modes (Python, Pandas, Spark, Spark SQL, Ray, SQL, Substrait)
• Explains ComputeEngine architecture (LocalComputeEngine, SparkComputeEngine) with DAG-based execution
• Includes mermaid diagrams for architecture and feature build flow
• Provides migration guide from legacy On Demand Feature Views
• Contains real-world use cases and code examples
• Authors: @HaoXuAI and GitHub Copilot

Documentation Updates (docs/getting-started/architecture/feature-transformation.md)

• Added callout linking to blog post
• Documented available TransformationMode options with use case guidance

Example Usage

from feast.transformation.base import transformation
from feast.transformation.mode import TransformationMode

# Define transformation with decorator
@transformation(mode=TransformationMode.SPARK)
def transform_features(df: DataFrame) -> DataFrame:
    return df.withColumn("scaled", df["feature"] * 2)

# Apply to FeatureView
feature_view = FeatureView(
    name="driver_stats",
    feature_transformation=transform_features,
    schema=[...],
    source=data_source,
)

Which issue(s) this PR fixes:

Addresses documentation request for transformation framework work from PRs #5181, #5223, #5278, #5185, #5281, #5287, #5354, #5445, #5521, #5523, #5666, #5611, #5612, #5502, #5650, #5629

Misc

Blog post covers architectural improvements that unify feature transformation logic across compute engines while maintaining backward compatibility with existing APIs.

---

This section details on the original issue you should resolve

<issue_title>Add blog post on new transformation framework</issue_title>
<issue_description>Is your feature request related to a problem? Please describe.
I want a blog post on the website that outlines the new transformation framework in feast. Please see these PRs:

• feat: Kickoff Transformation implementationtransformation code base #5181
• feat: Compute Engine Initial Implementation #5223
• feat: Local compute engine #5278
• feat: Spark Transformation #5185
• feat: Offline store update pull_all_from_table_or_query to make timestampfield optional #5281
• feat: Enable write node for compute engine #5287
• feat: Refactor materialization engine #5354
• feat: Update Spark Compute read source node to be able to use other data sources #5445
• feat: Update doc #5521
• feat: Continue updating doc #5523
• feat: Support aggregation in odfv #5666
• feat: Feast dataframe phase1 #5611
• feat: Feast dataframe phase2 #5612
• fix: FeatureView serialization with cycle detection #5502
• feat: Support table format: Iceberg, Delta, and Hudi #5650
• feat: Add aggregation in OnDemandFeatureView #5629

Describe the solution you'd like
Please make sure the blog post is under infra/website/docs/blog and it would probably good to update /docs if needed.

Feel free to add a mermaid diagram or so. Please list @HaoXuAI and GitHub Copillot as the authors.
</issue_description>

<agent_instructions>I want a blog post on the website that outlines the new transformation framework in feast. Please see these PRs:

• feat: Kickoff Transformation implementationtransformation code base #5181
• feat: Compute Engine Initial Implementation #5223
• feat: Local compute engine #5278
• feat: Spark Transformation #5185
• feat: Offline store update pull_all_from_table_or_query to make timestampfield optional #5281
• feat: Enable write node for compute engine #5287
• feat: Refactor materialization engine #5354
• feat: Update Spark Compute read source node to be able to use other data sources #5445
• feat: Update doc #5521
• feat: Continue updating doc #5523
• feat: Support aggregation in odfv #5666
• feat: Feast dataframe phase1 #5611
• feat: Feast dataframe phase2 #5612
• fix: FeatureView serialization with cycle detection #5502
• feat: Support table format: Iceberg, Delta, and Hudi #5650
• feat: Add aggregation in OnDemandFeatureView #5629

Please make sure the blog post is under infra/website/docs/blog and it would probably good to update /docs if needed. Also, please make sure to look at the existing documentation before updating.

Feel free to add a mermaid diagram or so. Please list @HaoXuAI and GitHub Copillot as the authors.
</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Add blog post on new transformation framework #5856

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