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SECTION 0 — PERFORMANCE IS ONE PIPELINE

Users experience performance as one thing.

Your system is a pipeline:

Network → CDN → Server → DB → Response → Render → Hydrate → Interact

Senior fullstack performance means you manage budgets across that pipeline.

SECTION 1 — LATENCY BUDGETING (THE MODEL)

Pick targets:

  • TTFB p95

  • LCP p75

  • INP p75

Then allocate budgets:

  • server compute

  • DB/query time

  • cache hit rate targets

  • client render/hydration

Senior rule:

If you don’t budget, you will overspend unpredictably.

SECTION 2 — WHAT TO MEASURE FIRST (ANTI-PLACEBO)

Start with:

  • end-to-end traces for slow requests

  • DB query timings + frequency

  • cache hit rates

  • payload sizes (JSON, images)

Avoid:

  • “micro-optimizations” without a measured bottleneck

SECTION 3 — CACHING HIERARCHY

Layers:

  1. browser (assets)

  2. CDN (cacheable GETs)

  3. server/app cache (hot computed results)

  4. DB/query cache (where appropriate)

Keys:

  • include auth scope

  • include tenantId

  • include version

Invalidation:

  • prefer event-driven invalidation for correctness-critical data

  • otherwise TTL + stale-while-revalidate

Stampede control:

  • request coalescing

  • jittered TTL

  • soft/hard TTL

SECTION 4 — PAYLOAD BUDGETS (FRONTEND IS BACKEND TOO)

Large payloads kill:

  • mobile networks

  • render time

  • memory

Senior tactics:

  • pagination and windowing

  • field selection (don’t ship unused fields)

  • compress responses

  • image resizing and modern formats

SECTION 5 — RENDERING STRATEGIES (SSR/CSR/STREAMING)

Rules of thumb:

  • SSR for fast first content

  • CSR for highly interactive subtrees

  • streaming when you can progressively reveal content

But always measure real user metrics.

SECTION 6 — PROFILING PLAYBOOK

  1. Reproduce slow path (prod traces > local guessing)

  2. Identify bottleneck category: IO, DB, CPU, serialization, client render

  3. Fix the bottleneck (one change)

  4. Measure again

SECTION 7 — EXERCISES

  1. Define budgets for one critical page (TTFB/LCP/INP).

  2. List your caching layers and which data belongs in each.

  3. Pick one endpoint and cut payload size by 30% (design how).

🏁 END — END-TO-END PERFORMANCE BUDGETS