Databases
Firestore
Serverless NoSQL document database
AWS equivalent
DynamoDB
AWS → GCP: Key Differences
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Document model (like MongoDB) rather than DynamoDB's key-value/wide-column hybrid.
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Real-time listeners: clients can subscribe to query results and get updates instantly.
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Fully serverless: no capacity mode to choose, no read/write units to configure.
Key Concepts to Know
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Document model: collections → documents → fields. Supports nested subcollections.
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Automatic scaling: handles millions of concurrent connections.
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Strong consistency for single-document reads in Native mode.
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Transactions and batch writes for atomic multi-document operations.
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Free tier: 1GB storage, 50K reads, 20K writes per day — good for prototyping.
DCE Interview Tips
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Use Firestore for: mobile/web app backends, user profiles, real-time features (chat, live dashboards), session data.
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Firestore vs Bigtable: 'Firestore for transactional, document-oriented workloads needing real-time sync. Bigtable for analytics and high-throughput operational workloads.'
Common Gotchas
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Firestore has a 1 write/second per document limit. For high-frequency counter updates, use distributed counters.
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Not ideal for analytical queries — use BigQuery for that.