Key Architectural Trade-offs

• Presigned direct-to-blob uploads take the bytes off your API tier entirely, at the cost of a more complex client and a post-upload validation step.
• Eager derivative generation makes every view fast and wastes compute on posts nobody sees; lazy generation is cheap and adds first-view latency.
• Engagement counters in the post row cause write hotspots on viral content — sharded counters or an approximate counter service trade exactness for survivability.