Technology Fundamentals 4: A Practical Overview

Screening is designed for people who may have an infection without knowing it; many STIs cause no noticeable symptoms. If someone has symptoms or has been told they may have been exposed, that is different from routine screening and should be discussed with a clinician. A screening appointment may need to include an assessment beyond the tests usually offered to someone without symptoms.

You can often replace a coordination problem with an idempotency key. That applies to cloud infrastructure as well. In practice, cloud infrastructure behaves differently: Anything that grows without a bound will eventually hit one. Documentation that is not tested tends to describe the previous version. The same reasoning holds for cloud infrastructure.

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

Rate Limiting: A queue smooths spikes but also hides how far behind you are. Rate Limiting: Retries without jitter turn a small outage into a large one. Rate Limiting: Separating the reads from the writes buys room to change either side.

For access control, the constraint matters more than the feature list. Periodic jobs should be safe to run twice, because they will be. Teams working on access control usually discover this the hard way. You rarely need a new component to fix a boundary problem. The signal you want is often already logged, just not aggregated. This is most visible in access control.

Monitoring Alerts: The first thing to settle is the failure mode, not the happy path. Monitoring Alerts: Measurements taken once are anecdotes; you need a baseline that repeats. Monitoring Alerts: Costs usually concentrate in a small number of operations, so find those first.

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.

The interesting number is not the average, it is the 99th percentile. That applies to api design as well. In practice, api design behaves differently: Adding a cache in front of a slow query is a fix; fixing the query is a cure. Every abstraction you add is a place where behaviour can differ from intent. The same reasoning holds for api design.

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

A queue smooths spikes but also hides how far behind you are. This is most visible in release process. Consider release process specifically. Retries without jitter turn a small outage into a large one. Release Process: Separating the reads from the writes buys room to change either side.

Observability: The first thing to settle is the failure mode, not the happy path. Observability: Measurements taken once are anecdotes; you need a baseline that repeats. Observability: Costs usually concentrate in a small number of operations, so find those first.

Configurations should be reviewable in a diff, not only in a console. This is most visible in schema migration. Consider schema migration specifically. The best time to add an index is before the table gets large. Schema Migration: 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.

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

Serving static bytes is the cheapest thing you can do at the edge. That applies to schema markup as well. In practice, schema markup behaves differently: A schema is an interface; changing it is a migration, not an edit. Track the denominator as carefully as the numerator. The same reasoning holds for schema markup.

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

For crawl budget, the constraint matters more than the feature list. Periodic jobs should be safe to run twice, because they will be. Teams working on crawl budget usually discover this the hard way. You rarely need a new component to fix a boundary problem. The signal you want is often already logged, just not aggregated. This is most visible in crawl budget.

Cost Controls: A queue smooths spikes but also hides how far behind you are. Cost Controls: Retries without jitter turn a small outage into a large one. Cost Controls: Separating the reads from the writes buys room to change either side.

Consent is an ongoing, voluntary agreement, not a one-time permission that applies to everything. It can be changed or withdrawn, and agreement to one activity does not automatically mean agreement to another. A person who is asleep or unable to make a clear, voluntary choice cannot provide consent; legal definitions and capacity rules vary by country. When either person seems uncertain, stop and ask rather than treating silence as agreement.

Consent also depends on capacity: a person must be able to understand the choice and communicate it. Alcohol or other drugs can affect judgment and awareness, and the effect differs from person to person. If someone seems confused, unconscious or too impaired to make or communicate a decision, do not proceed. Laws define capacity and consent differently across countries, so local legal guidance matters.

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

Consider release process specifically. If the rollback plan needs a meeting, it is not a rollback plan. Release Process: 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 release process as well.

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

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