Databases
229 bites tagged Databases — interview questions with model answers, and 60-second explainers.
ACID: The Four Guarantees of Database Transactions
ACID is a contract for database transactions: all-or-nothing guarantees for data validity, even during crashes. It's critical for relational databases in finance or e-commerce. The footgun is assuming all databases offer this; many NoSQL systems don't.
Primary Keys: The Unique ID for Every Row
A primary key is like a social security number for a database row, uniquely identifying it. It's used to reliably fetch records and link related data across tables. The footgun is using a natural key, like an email address, that might change over time.
DBMS: The Software That Runs Your Database
A DBMS is the software engine that manages a database, separating your app from raw data files. You use it to query, update, and administer data, like with PostgreSQL or MySQL. The common footgun is confusing the DBMS with the database itself.
Data Partitioning: Spreading Data for Scalability
Partitioning splits a huge dataset across many machines, like assigning phonebook sections to different librarians. This allows systems to scale beyond a single server.
CAP Theorem: Pick Two of Three Guarantees
The CAP Theorem states a distributed system can only have two of three guarantees: Consistency, Availability, or Partition Tolerance. When the network fails (a partition), you must choose: stop responding to ensure data is consistent (CP) or keep responding…
AWS DMS: Automating Database Migrations
AWS DMS automates moving data between databases, not just as a simple data pump. Use it for one-time migrations to the cloud or for continuous replication. The footgun is assuming DMS also converts your schema; for different engines, you must use the Schema…
Managed In-Memory Data Store: Speed Without the Sysadmin
A managed in-memory store is a high-speed valet for your data, sitting between your app and database to serve requests at microsecond latency. Use it for database acceleration or session stores. The footgun is treating it as a permanent database.
Managed Databases: Let the Cloud Handle Ops
A managed database is like leasing a car with a full-service plan instead of fixing it yourself; you trade control for convenience. This is the model for AWS RDS or GCP Cloud SQL.
Eventual Consistency: Availability Over Immediacy
Eventual consistency trades immediate correctness for high availability. It's used in distributed systems where being online is critical. The footgun is assuming "eventual" implies a specific timeframe; it only guarantees convergence if updates cease.
Data Aggregation: The Big Picture from Small Details
Data aggregation rolls up granular records into high-level summaries, like turning individual sales logs into a daily sales report. It's used to power dashboards and speed up warehouse queries.
Data Dictionary: The 'About' Page for Your Data
A data dictionary is the instruction manual for your database, defining what each piece of data means and how it's formatted. It's used by engineers to understand a schema or by analytics tools to interpret columns. The biggest footgun is letting it go stale.
Change Data Capture (CDC): Turn Your Database Into a Stream
Change Data Capture (CDC) turns your database into a real-time stream of change events (inserts, updates, deletes). It's used to sync data across systems, like updating search indexes or feeding analytics warehouses, without full table scans.
Online Analytical Processing (OLAP)
OLAP databases are built to quickly answer complex, multi-dimensional questions, unlike transactional (OLTP) databases that handle individual records. They power business intelligence tools for sales and marketing analysis.
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