Q1. What is the difference between a query, a mutation and a subscription?
- Query: a read operation. Queries can run in parallel and must be side-effect free. - Mutation: a write operation that changes server state. Top-level mutation fields ru...
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Q2. What is the difference between a clustered and a non-clustered index?
A clustered index defines the physical order of rows in the table. Because the data is stored in that order, a table can have only one clustered index, usually the primar...
Q3. How does BigQuery separate storage and compute?
BigQuery is a serverless, columnar data warehouse built on a separation of storage and compute. - Storage: data lives in Capacitor, a columnar format backed by Colossus d...
Q4. What is deferred execution in LINQ and why does it matter?
LINQ queries over `IEnumerable` are lazy: the query is a description that runs only when enumerated by `foreach`, `ToList`, `Count`, `First` or similar. Each enumeration ...
Q5. How would you analyse and optimise a slow query?
Query optimisation starts by measuring. `EXPLAIN` shows the plan; `EXPLAIN ANALYZE` runs it and reports actual rows and time. Things to look for: sequential scans on larg...
Q6. How do you optimise BigQuery query cost and performance?
Cost in on-demand BigQuery is driven by bytes scanned, so reduce what each query reads. - Partition tables, usually by date, and add partition filters so only relevant pa...
Q7. How do you design filtering, sorting and sparse fieldsets?
Expose them as query parameters with a clear convention: ```http GET /articles?status=published&author=42&sort=-created_at&fields=id,title ``` - Filtering: one parameter ...