Seb Armand told some battle stories of how they have approached scaling Laravel at Square, one of the largest payment processors.

• Reducing database load: eager-loading queries, using Elasticache, developing Tag Tree Cache to cache multiple levels and recursively flush the relevant caches
• Reducing bandwidth: using CDNs to move assets closer to end users
• Reducing processing: using queues and deduplication
• Further reducing processing: using batches and pipelines, and buffering/bundling tasks together