DataEngPrep.tech
QuestionsBlogStore
Get PDF Bundle
Home/Questions/Spark/Big Data/A JSON file with evolving schema needs to be ingested into a DataFrame. How would you handle new fields dynamically in PySpark without breaking the job for previous structures?

A JSON file with evolving schema needs to be ingested into a DataFrame. How would you handle new fields dynamically in PySpark without breaking the job for previous structures?

Spark/Big Dataeasy0.3 min readPremium
Frequency
Low
Asked at 1 company
Category
452
questions in Spark/Big Data
Difficulty Split
88E|81M|283H
in this category
Total Bank
1,863
across 7 categories
Asked at these companies
Dunnhumby
Key Concepts Tested
spark
Expert AnswerPremium
52 wordsInterview-ready
Use schema-on-read with mergeSchema: df = spark.read.option("mergeSchema", "true").json("s3://bucket/events/"). **Why**: New fields appear as null in old records; no job failure. **Production**: Schema registry or versioned schemas; explicit schema with allowNull for new columns; from_json with optional fields. **Scalability**: mergeSchema has overhead; use for bounded evolution....
The complete answer continues with detailed implementation patterns, architectural trade-offs, and production-grade considerations. It covers performance optimization strategies, common pitfalls to avoid, and real-world examples from companies like Dunnhumby. The answer also includes follow-up discussion points that interviewers commonly explore.

Continue Reading the Full Answer

Unlock the complete expert answer with code examples, trade-offs, and pro tips - plus 1,863+ more.

Create Free Account - Unlock 30 Answers
Get PDF Bundle - from $21

Or upgrade to Platform Pro - $39

Engineers who used these answers got offers at

AmazonDatabricksSnowflakeGoogleMeta

Free: Top 20 SQL Interview Questions (PDF)

Get the most asked SQL questions with expert answers. Instant download.

No spam. Unsubscribe anytime.

Related Spark/Big Data Questions

mediumWhat is the difference between repartition and coalesce in Apache Spark?FreehardWhat is the difference between SparkSession and SparkContext in Spark?FreemediumWhat is the difference between cache() and persist() in Spark? When would you use each?FreemediumWhat is the difference between groupByKey and reduceByKey in Spark?FreemediumWhat is the difference between narrow and wide transformations in Apache Spark? Explain with examples.Free

According to DataEngPrep.tech, this is one of the most frequently asked Spark/Big Data interview questions, reported at 1 company. DataEngPrep.tech maintains a curated database of 1,863+ real data engineering interview questions across 7 categories, verified by industry professionals.

← Back to all questionsMore Spark/Big Data questions →