Replication, Partitioning, and Sharding

Scaling and distributing data across nodes: primary-replica and multi-primary replication, read-replica scaling, horizontal partitioning, and sharding strategies with their key-selection and rebalancing challenges. Covers replication lag, routing, and the operational cost of a partitioned topology. Key to designing databases that scale horizontally.

98 questions

Storage Systems and Infrastructure

The physical and infrastructure layer beneath databases: disk and volume management, storage redundancy and RAID levels, storage services, and how storage architecture affects durability and performance. Covers matching storage configuration to reliability and throughput requirements. Serves infrastructure and systems roles that own the hardware substrate.

1 questions

Database Performance Tuning and Scaling

System-level performance work beyond a single query: configuration and resource tuning, capacity planning, handling large data volumes, and scaling read and write throughput. Covers identifying bottlenecks, growth management, and the vertical-versus-horizontal scaling decision. Tests whether a candidate can keep a database healthy as load grows.

85 questions

Data Warehousing and Dimensional Modeling

Analytical data platforms: star and snowflake schemas, fact and dimension tables, slowly changing dimensions, and cloud data warehouse design and optimization (Redshift, BigQuery, Snowflake-style systems). Covers modeling for analytics versus transactions and tuning warehouse query performance. Central to data-engineering and BI interviews.

10 questions

Geospatial and Time-Series Data

Specialized data shapes and their stores: geospatial data types, spatial indexing, and location queries; and time-series data with high-ingest, retention, and downsampling patterns. Covers when purpose-built extensions or databases beat general-purpose stores for these workloads. A niche but recurring topic for location- and telemetry-heavy systems.

5 questions

SQL Dialects and Built-in Functions

Portability and idiom differences across SQL engines (PostgreSQL, Redshift, MySQL, SQL Server, and others), plus fluent use of built-in string, date/time, and type-conversion functions. Covers dialect-specific syntax, function availability, and writing queries that behave predictably across platforms. Relevant when candidates move between database ecosystems.

7 questions

SQL Joins and Set Operations

Combining data across multiple tables using inner, outer, cross, and self joins, plus set operations (UNION, INTERSECT, EXCEPT). Covers join-key selection, fan-out and row-multiplication pitfalls, merge strategies, and integrating data from disparate sources. A high-frequency interview surface for anyone who queries relational data.

45 questions

Database Monitoring, Troubleshooting, and Diagnostics

Observing and fixing databases in production: health checks, metrics and alerting, and diagnosing common failures like slow queries, lock contention, replication lag, and resource exhaustion. Covers a systematic troubleshooting method under incident pressure. Tests operational instincts distinct from design knowledge.

6 questions

Caching and Connection Management

The layer between application and database: cache strategies (cache-aside, write-through, invalidation) for query results, connection pooling and lifecycle, and efficient application-to-database interaction. Covers reducing database load, avoiding pool exhaustion, and the consistency trade-offs caching introduces. Bridges application performance and database health.

4 questions

Data Modeling and Schema Design

Designing relational schemas end to end: entity-relationship modeling, normal forms and deliberate denormalization, primary/foreign keys, data types, and integrity constraints, together with applied schema design driven by real business requirements and query access patterns. Covers modeling a domain from ambiguous requirements, choosing structures that serve the queries a system must run, trading normalization for correctness against denormalization for read performance, and evolving schemas as needs change. Foundational data-modeling judgment for building and reviewing databases, tested through open-ended domain-modeling prompts.

105 questions

Database Administration and Operations

Day-to-day operation of database systems: configuration and tuning, patching and upgrades, automation and scripting, standards and best practices, and capacity/growth management. Covers the responsibilities of keeping databases reliable, secure, and maintainable in production. The operational-ownership surface for DBA and platform roles.

33 questions

Cloud and Managed Database Services

Running databases on cloud platforms: managed relational and NoSQL offerings, cloud storage and database options (e.g. Azure, AWS), and the trade-offs of managed services versus self-managed instances. Covers provisioning, scaling, cost, and integration with the surrounding cloud ecosystem. Relevant to cloud-focused engineering and architecture roles.

0 questions

Indexing Strategy and Design

Choosing and designing indexes: B-tree, hash, composite, covering, and partial indexes, and the trade-offs between read acceleration and write/storage overhead. Covers selecting index columns from query patterns, cardinality and selectivity reasoning, and diagnosing why an index is or is not used. Central to database performance interviews.

51 questions

Database Forensics and Data Recovery

Investigative and recovery work on databases: examining database and application artifacts, transaction logs, and residual data to reconstruct activity, plus recovering corrupted or deleted data. Covers evidence integrity and forensic method applied to database systems. A specialized surface for security and forensics roles.

0 questions

Backup and Disaster Recovery

Keeping data durable and recoverable when systems fail: backup design (full, incremental, differential, and snapshot strategies; point-in-time recovery), backup verification and restore testing, retention and archival policy (including compliance retention and legal holds), encryption and key management for backups, and disaster-recovery planning measured against recovery-time and recovery-point objectives (RTO/RPO). Tests whether a candidate can design a backup strategy that actually restores, choose the right retention tier for a business's downtime and data-loss tolerance, and operate backup systems safely under failure, compliance, and ransomware threats. Distinct from code-level fault-tolerance patterns (circuit breakers, retries, bulkheads) and multi-region failover architecture, which belong to high-availability-and-disaster-recovery.

6 questions

Consistency Models and Distributed Databases

Data correctness across distributed systems: strong versus eventual consistency, the CAP and PACELC trade-offs, consensus and quorum reads/writes, and consistency-versus-availability decisions. Covers how distributed databases reconcile replicas and what guarantees applications can rely on. A staple of distributed-systems and architecture interviews.

15 questions

SQL Query Fundamentals

Core SQL for reading and shaping data: SELECT, filtering with WHERE, sorting, DISTINCT, and single-table aggregation with GROUP BY, HAVING, and aggregate functions. Covers reasoning about NULL handling, grouping semantics, and writing correct queries against a given schema. The baseline query-writing surface most data and engineering interviews open with.

78 questions

Query Optimization and Execution Plans

Making queries fast: reading and interpreting execution/explain plans, identifying full scans, spotting SQL anti-patterns, and rewriting queries for better performance. Covers how the planner chooses join order and access methods, and how statistics drive those choices. A core skill for anyone responsible for query performance in production.

66 questions

Advanced SQL: Window Functions, CTEs, and Subqueries

Analytical SQL for complex problems: window functions (ranking, running totals, LAG/LEAD, partitioned aggregates), common table expressions including recursive CTEs, and scalar, nested, and correlated subqueries. Covers when each construct is the right tool and how they compose for multi-step analysis. The differentiator between basic and senior SQL competence.

74 questions

Transactions, Concurrency Control, and Isolation Levels

How databases manage concurrent access: ACID transactions, isolation levels and the anomalies they permit (dirty/non-repeatable/phantom reads), locking, and optimistic versus pessimistic concurrency. Covers deadlock handling and choosing an isolation level for a workload. Essential for correctness in any multi-user database system.

9 questions

Database Selection and Trade-offs

Choosing the right database and data platform for a workload: relational versus NoSQL versus specialized stores, managed versus self-hosted, and matching technology to consistency, scale, cost, and query needs. Covers structuring the decision, naming trade-offs, and defending a recommendation. A judgment-heavy interview surface for architects and senior engineers.

54 questions

NoSQL and Polyglot Persistence

Non-relational data stores and mixing them: key-value, document, wide-column, and graph databases, their data models and access patterns, and polyglot persistence where different stores serve different needs. Covers when NoSQL beats relational and how to integrate multiple stores coherently. Increasingly common in system-design and data-platform interviews.

2 questions

Database Internals and Storage Engines

How databases work under the hood: storage-engine architectures (B-tree versus LSM-tree), on-disk page and buffer management, write-ahead logging, and MVCC. Covers the engine-level mechanisms that explain performance, durability, and concurrency behavior. Tests depth beyond usage — why a database behaves as it does.

40 questions

Database Engineering & Data Systems Topics