Integration / Apache NiFi Interview Questions

What is the LookupRecord processor used for?

LookupRecord is a record-aware NiFi processor that enriches records within a FlowFile by looking up values from an external source — a database, a distributed map cache, a REST API, or a file-based lookup table — and adding the result as a new field in each record.

LookupRecord works with three components:

RecordReader: Parses the incoming FlowFile into records.

RecordWriter: Serializes enriched records back to the output FlowFile.

LookupService Controller Service: The enrichment data source. Implementations include:

SimpleCsvFileLookupService: Looks up values from an in-memory CSV file — useful for small static reference tables.
IPLookupService: GeoIP enrichment from a MaxMind database.
DatabaseRecordLookupService: Executes a parameterized SQL query against a JDBC source for each lookup.
DistributedMapCacheLookupService: Looks up values from a distributed in-memory cache populated by another part of the flow.
RestLookupService: Calls a REST API endpoint for each lookup.

Configuration specifies which record fields are the lookup key(s) and which path in the output record receives the looked-up value. When no match is found, the processor routes to the unmatched relationship for separate handling.

Take quiz

Which LookupRecord LookupService would you use to add GeoIP country and city information to network log records?SimpleCsvFileLookupService

✗ Try again — a CSV file cannot practically contain all IP ranges for GeoIP enrichment.

IPLookupService with a MaxMind GeoIP database

✓ Well done — IPLookupService uses the MaxMind GeoLite2 or GeoIP2 database to enrich IP addresses with geographic and ASN information.

DatabaseRecordLookupService with a SQL SELECT on each IP

✗ Try again — querying a database per record would be extremely slow for high-volume network logs; IPLookupService uses an in-memory database optimized for IP range lookups.

To which relationship does LookupRecord route records for which no match was found in the LookupService?failure

✗ Try again — failure is for processing errors; unmatched lookups are a distinct, non-error case with their own relationship.

unmatched

✓ Well done — unmatched allows you to handle records with no lookup result differently from both matched records and processing failures.

not-found

✗ Try again — the actual relationship name is unmatched, not not-found.

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Integration / Apache NiFi Interview Questions

What is the LookupRecord processor used for?

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