Common Mistakes When Evaluating Edge Caching

Storage Tiers: The interesting number is not the average, it is the 99th percentile. Storage Tiers: Adding a cache in front of a slow query is a fix; fixing the query is a cure. Storage Tiers: Every abstraction you add is a place where behaviour can differ from intent.

Data Pipelines: If a metric has no owner, it will drift until it causes an incident. Data Pipelines: The cheapest optimisation is usually removing work nobody asked for. Data Pipelines: Aggregating at write time trades flexibility for predictable read cost.

Data Pipelines: Periodic jobs should be safe to run twice, because they will be. Data Pipelines: You rarely need a new component to fix a boundary problem. Data Pipelines: The signal you want is often already logged, just not aggregated.

Data Pipelines: Configurations should be reviewable in a diff, not only in a console. The best time to add an index is before the table gets large. That applies to data pipelines as well. In practice, data pipelines behaves differently: Failures are usually correlated, so plan for the shared dependency.

Use statements about your own needs rather than trying to guess your partner’s intentions. You might say, “I’m comfortable with this, but not with that,” or, “I need us to stop if I say pause.” Be specific about what you mean by words such as “slow down” or “check in.” Ask your partner what they are comfortable with, and leave room for an answer without interrupting or arguing.

For load balancing, the constraint matters more than the feature list. The first thing to settle is the failure mode, not the happy path. Teams working on load balancing usually discover this the hard way. Measurements taken once are anecdotes; you need a baseline that repeats. Costs usually concentrate in a small number of operations, so find those first. This is most visible in load balancing.

Observability: If a metric has no owner, it will drift until it causes an incident. Observability: The cheapest optimisation is usually removing work nobody asked for. Observability: Aggregating at write time trades flexibility for predictable read cost.

If a metric has no owner, it will drift until it causes an incident. This is most visible in monitoring alerts. Consider monitoring alerts specifically. The cheapest optimisation is usually removing work nobody asked for. Monitoring Alerts: Aggregating at write time trades flexibility for predictable read cost.

A design that cannot be rolled back is a design that cannot be changed safely. The same reasoning holds for content delivery. For content delivery, the constraint matters more than the feature list. Latency budgets are easier to defend when every hop has a stated ceiling. Teams working on content delivery usually discover this the hard way. Caching helps only until the invalidation rules become the bottleneck.

Consent is not a one-time permission that applies to everything that follows. Agreement to one activity does not automatically mean agreement to another, and consent on one occasion does not establish consent on a later occasion. People can set limits, ask to pause or change their minds at any point. The other person needs to respect that change without argument or pressure.

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The interesting number is not the average, it is the 99th percentile. The same reasoning holds for edge caching. For edge caching, the constraint matters more than the feature list. Adding a cache in front of a slow query is a fix; fixing the query is a cure. Teams working on edge caching usually discover this the hard way. Every abstraction you add is a place where behaviour can differ from intent.

Data Pipelines: Serving static bytes is the cheapest thing you can do at the edge. Data Pipelines: A schema is an interface; changing it is a migration, not an edit. Data Pipelines: Track the denominator as carefully as the numerator.

Rate Limiting: Configurations should be reviewable in a diff, not only in a console. Rate Limiting: The best time to add an index is before the table gets large. Rate Limiting: Failures are usually correlated, so plan for the shared dependency.

Consider log analysis specifically. If the rollback plan needs a meeting, it is not a rollback plan. Log Analysis: Small pages that stay small are easier to keep fast than large ones made fast. Write the invariant down; otherwise it lives only in someone's memory. That applies to log analysis as well.

Load Balancing: You can often replace a coordination problem with an idempotency key. Load Balancing: Anything that grows without a bound will eventually hit one. Load Balancing: Documentation that is not tested tends to describe the previous version.

Teams working on content delivery usually discover this the hard way. If the rollback plan needs a meeting, it is not a rollback plan. Small pages that stay small are easier to keep fast than large ones made fast. This is most visible in content delivery. Consider content delivery specifically. Write the invariant down; otherwise it lives only in someone's memory.

Load Balancing: If a metric has no owner, it will drift until it causes an incident. Load Balancing: The cheapest optimisation is usually removing work nobody asked for. Load Balancing: Aggregating at write time trades flexibility for predictable read cost.

Configurations should be reviewable in a diff, not only in a console. This is most visible in edge caching. Consider edge caching specifically. The best time to add an index is before the table gets large. Edge Caching: Failures are usually correlated, so plan for the shared dependency.

Access Control: Periodic jobs should be safe to run twice, because they will be. Access Control: You rarely need a new component to fix a boundary problem. Access Control: The signal you want is often already logged, just not aggregated.

Queue Design: The first thing to settle is the failure mode, not the happy path. Measurements taken once are anecdotes; you need a baseline that repeats. That applies to queue design as well. In practice, queue design behaves differently: Costs usually concentrate in a small number of operations, so find those first.

Load Balancing: Serving static bytes is the cheapest thing you can do at the edge. Load Balancing: A schema is an interface; changing it is a migration, not an edit. Load Balancing: Track the denominator as carefully as the numerator.

Monitoring Alerts: Periodic jobs should be safe to run twice, because they will be. You rarely need a new component to fix a boundary problem. That applies to monitoring alerts as well. In practice, monitoring alerts behaves differently: The signal you want is often already logged, just not aggregated.

Schema Migration: Serving static bytes is the cheapest thing you can do at the edge. Schema Migration: A schema is an interface; changing it is a migration, not an edit. Schema Migration: Track the denominator as carefully as the numerator.