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2948 questions of the kind that actually get asked — in interviews, in architecture review boards, and by the person who has to run the thing at 3 AM. Every answer states the trade-off rather than the slogan, and says when the obvious choice is the wrong one.

All areas2948 Architecture Fundamentals91 Distributed Systems101 Data Architecture90 Cloud Architecture87 Networking96 API & Integration Architecture87 Reliability & Resilience99 Observability92 Performance & Capacity Engineering100 Security Architecture105 Cost Architecture & FinOps102 Business Architecture103 Architecture Communication102 Enterprise Architecture100 Legacy Modernization102 AI-Era Architecture106 Software Architecture & Engineering93 Architecture Patterns94 Architecture Decision-Making101 The Architect's Meta-Skills102 Delivery & Release Engineering103 Platform Engineering & Developer Experience102 Testing & Quality Architecture102 Data Platform Architecture98 Streaming & Real-Time Data103 Data Governance & Semantics91 Frontend & Experience Architecture101 Edge, Mobile & IoT98 Regulatory & Data Protection Architecture99 Assurance, Audit & Model Risk98
Difficulty Any beginner intermediate advanced

6 questions in SQL vs NoSQL.

  1. SQL vs NoSQL advanced

    A platform must choose between a relational database and a wide-column store for its highest-volume data. What decides it, and what is the common error?

    2 min answer sqlnosqlaccess-patternspartition-key
  2. SQL vs NoSQL advanced

    A startup with a few thousand users is choosing between a single-region Postgres and a geo-distributed serializable database. What evidence should drive the decision, and what would trigger revisiting it?

    3 min answer cockroachdbpostgresdistributed-sqlreversibility
  3. SQL vs NoSQL intermediate

    A team proposes a document database for an order management system because "orders are documents". Assess.

    2 min answer datastoredecisionmodelling
  4. SQL vs NoSQL advanced

    By 2021 Notion's single Postgres database had reached the point where VACUUM stalled and transaction ID wraparound became a genuine risk. They sharded Postgres into 480 logical shards rather than moving block data to a NoSQL store. What forced the change, what decided the destination, and where would copying it be a mistake?

    2 min answer notionpostgresshardingvacuum
  5. SQL vs NoSQL advanced Multiple choice

    Discord's message store reached trillions of rows on a Cassandra cluster reported at 177 nodes; in 2023 it published a move to ScyllaDB and placed Rust data services in front of the store whose main job is request coalescing. Messages are partitioned by channel id plus a time bucket. Which property of the workload best explains why the answer was a different wide-column engine plus a coalescing layer rather than a relational sharding tier?

    3 min answer discordscylladbcassandrahot-partition
  6. SQL vs NoSQL advanced Multiple choice

    Figma's Postgres stack grew roughly 100x between 2020 and 2024. The team had already partitioned tables vertically and now needed horizontal scale for the largest tables. They evaluated distributed SQL engines including CockroachDB and TiDB and rejected all of them, then spent about nine months building their own sharding layer with a query proxy written in Go. Which fact best explains that choice?

    2 min answer figmapostgresshardingtechnology-selection