System design examples (Java)

A bunch of small, runnable Java/Spring projects that mirror common system design interviews.

Projects (index)

• URL shortener (Bitly-style) — evolves from “works on my laptop” to “scales reads” (HelloInterview: https://www.hellointerview.com/learn/system-design/problem-breakdowns/bitly)

  • Overview: shortUrl
  • Features:
    • In-memory: shortUrl/simplestVersion
    • Database-backed: shortUrl/databaseVersion
    • Internal (in-process) cache: shortUrl/internalCachedVersion
    • External cache (Redis): shortUrl/externalCachedVersion

• Dropbox-style file storage & sync — upload flows + chunking + dedupe (HelloInterview: https://www.hellointerview.com/learn/system-design/problem-breakdowns/dropbox)

  • Overview: dropbox
  • Features:
    • Naive server-proxied upload: dropbox/simplestVersion
    • Presigned direct-to-S3: dropbox/directS3
    • Multipart upload reference: dropbox/multipartUpload
    • Content-addressed chunks: dropbox/chunkS3
    • Rolling/content-defined chunking: dropbox/rollingChunks

• External cache + observability (DynamoDB example) — a tiny app showing “slow vs cached” reads with metrics

• Local delivery (GoPuff-style) — geo lookups + caching + read scaling (based on the HelloInterview breakdown: https://www.hellointerview.com/learn/system-design/problem-breakdowns/gopuff)

  • Overview: localDelivery
  • Features:
    • Postgres + PostGIS geo queries: localDelivery/postgresGeo
    • Redis GEO geo queries: localDelivery/redisGeo
    • Redis grid caching for fast reads: localDelivery/cachingWithRedisGeo
    • Postgres read replicas: localDelivery/postgresReadReplicas
    • Cache + read replicas together: localDelivery/cacheWithReadReplicas
    • Simple end-to-end service: localDelivery/simpleLocalDeliveryService
    • More optimized end-to-end service: localDelivery/optimizedLocalDeliveryService

• Ticketmaster UNDER DEVELOPMENT (based on hellowInterview: Ticketmaster)

under development for now see ticketmaster