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Designs with worked examples 4

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3. Design a Distributed Cache
Partition cached data, survive node loss and keep cache misses from overwhelming the source of truth.
ClassicMedium
Caching Sharding Databases
+9
Distributed systems AWS Consistency Consistent hashing Hot keys LRU eviction Memcached Redis Replication
Worked design
Practice
30. Transactional Outbox
A service commits to its database and then publishes an event. If it dies in between, the row exists and no one hears about it. Publishing first has the mirror problem: an event for a write that never happened. There is no ordering of two independent systems that makes this safe.
Product & backendMedium
Queues Streaming Transactions
+5
Distributed systems Change data capture Consistency Kafka Outbox
Worked design
Practice
58. Design a Dating App like Tinder
Stacks of nearby people in under 300 ms, 2 billion swipes a day, and a match never missed even when both like at once.
ClassicMedium
Caching Databases Search
+7
AWS Bloom filter Consistency DynamoDB Geospatial OpenSearch Redis
Worked design
Practice
79. Design Object Storage like Amazon S3
An S3-inspired object store: bytes before metadata, a partitioned namespace with cache coherence, then repair, heat, lifecycle and safe change. Three interview boards with explicit assumptions and AWS source boundaries.
ClassicMedium
Object storage AWS Consistency
+2
Erasure coding Amazon S3
Worked design
Practice

Each design brings together the brief, practice, examples and discussion.