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Plaid·Software Engineer·Technical Phone Screen·Senior

SeniorPrefer not to say
Jun 2026Remote

Summary

Plaid data engineering interview that threw a deliberately messy, under-specified data problem at me. The core task was building a fuzzy bank-name mapping pipeline, and the ambiguity was very much the point. Walked away thinking I should have asked more clarifying questions upfront instead of diving straight into code.

Questions Asked (2)

Q1

Write a function that normalizes a raw bank name string into a canonical form, handling varying capitalization, punctuation, abbreviations, and corporate suffixes like 'N.A.', 'Inc.', and 'Corp.'.

Algorithms & Data StructuresTechnical Trade-offs
Author's notes

This part felt manageable.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and edge cases with the interviewer, then outline a pipeline: normalize case, remove punctuation, expand abbreviations, and strip corporate suffixes. Discuss trade-offs between rule-based and data-driven approaches, and mention scalability and maintainability.

Pro tip: Mention that normalization should be idempotent and consider using a configurable mapping for suffixes to easily update as new variations appear. Also, highlight the importance of testing with real-world messy data.

1. Clarify Requirements

Ask about the expected input format, output canonical form, and whether the function should handle international names or only US banks. Confirm if there's a predefined list of canonical names to map to.

2. Design Normalization Pipeline

Outline steps: convert to lowercase, remove punctuation and extra spaces, expand common abbreviations (e.g., 'N.A.' to 'NA'), and strip corporate suffixes like 'Inc', 'Corp', 'LLC'.

3. Handle Edge Cases and Variations

Consider abbreviations with periods, ampersands, and special characters. Decide whether to remove all punctuation or replace with spaces. Handle multiple suffixes and order variations.

4. Implement and Optimize

Write clean code with helper functions for each normalization step. Use regex for efficiency and consider precompiled patterns. Discuss time and space complexity.

5. Test and Validate

Propose test cases covering capitalization, punctuation, abbreviations, and suffixes. Suggest using a mapping table for canonical forms and validating against a sample dataset.

Key Points to Mention

  • Case normalization (lowercasing or uppercasing)
  • Punctuation removal or replacement (e.g., periods, commas, ampersands)
  • Abbreviation expansion (e.g., 'N.A.' to 'NA', 'Banc' to 'Bank')
  • Corporate suffix stripping (e.g., 'Inc', 'Corp', 'LLC', 'Ltd')
  • Trade-offs: rule-based vs. machine learning, maintainability vs. accuracy
  • Scalability: handling large volumes, caching, and idempotency

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.

Q2

Given cleaned bank name data with a non-1:1 mapping between internal and external bank IDs, write a fuzzy mapping function that returns all plausible external bank IDs for each internal bank ID rather than a single match.

Data ModelingTechnical Trade-offsAdaptability & Ambiguity
Author's notes

This is where it got uncomfortable.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the data characteristics and business requirements: what fields are available for matching, what similarity metrics make sense, and what threshold defines 'plausible'. Then outline a fuzzy matching pipeline that normalizes names, computes similarity scores, and returns all external IDs above a threshold, discussing trade-offs between recall and precision.

Pro tip: Emphasize that returning multiple matches is often safer than forcing a single match in ambiguous cases, but you must also provide confidence scores and a way to handle downstream ambiguity (e.g., manual review or weighted voting).

1. Clarify requirements and data

Ask about the available fields (e.g., bank name, routing number, address), the acceptable false positive/negative rates, and how the mapping will be used downstream.

2. Choose similarity metrics and normalization

Select appropriate string similarity measures (e.g., Levenshtein, Jaro-Winkler, token-based) and normalize names (lowercase, remove punctuation, handle abbreviations).

3. Define matching threshold and scoring

Set a similarity threshold (or multiple thresholds for confidence tiers) and compute a composite score if using multiple fields.

4. Return all plausible matches with scores

For each internal ID, return all external IDs whose similarity score exceeds the threshold, along with the scores for transparency.

5. Discuss trade-offs and validation

Explain how to evaluate precision/recall, handle performance at scale, and incorporate feedback loops for continuous improvement.

Key Points to Mention

  • Fuzzy matching algorithms (Levenshtein, Jaro-Winkler, TF-IDF, etc.) and their trade-offs
  • Threshold selection and its impact on precision vs. recall
  • Handling of abbreviations, punctuation, and common bank name variations
  • Scalability considerations (e.g., blocking, indexing, approximate nearest neighbors)
  • Returning confidence scores to enable downstream decision-making
  • Evaluation metrics and iterative refinement based on labeled data

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.