# Research ledger

Sources below were reported as opened by the named iteration; raw tool activity is preserved in its log.
- Iteration 1 · 2026-09-05 · [What is Amazon CloudFront?](https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/Introduction.html) — Edge delivery and origin retrieval in the CDN and caching questions.
- Iteration 1 · 2026-09-05 · [Use Elastic Load Balancing to distribute incoming application traffic in your Auto Scaling group](https://docs.aws.amazon.com/autoscaling/ec2/userguide/autoscaling-load-balancer.html) — Distinguishing load balancing from application-instance scaling.
- Iteration 1 · 2026-09-05 · [REL05-BP06 Make systems stateless where possible](https://docs.aws.amazon.com/wellarchitected/latest/framework/rel_mitigate_interaction_failure_stateless.html) — External session storage and authentication continuity after instance failure.
- Iteration 1 · 2026-09-05 · [Leadership Principles](https://www.amazon.jobs/content/en/our-workplace/leadership-principles) — Comparing the photographed 14-principle poster with the current 16 principles.
- Iteration 2 · 2026-09-05 · [Edit target group attributes for your Application Load Balancer](https://docs.aws.amazon.com/elasticloadbalancing/latest/application/edit-target-group-attributes.html#sticky-sessions) — Session affinity and authentication-failover interpretation for q-1788635240194-1.
- Iteration 2 · 2026-09-05 · [Amazon Machine Images in Amazon EC2](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/AMIs.html) — Reusable software configurations and preinstallation reasoning for startup questions, particularly q-1788635347056-1.
- Iteration 2 · 2026-09-05 · [Tenet 2. Be mindful of multicloud misconceptions](https://docs.aws.amazon.com/prescriptive-guidance/latest/strategy-multicloud/tenet-2.html) — Portability, exit requirements, and operational trade-offs for the three multi-cloud questions.
- Iteration 2 · 2026-09-05 · [REL13-BP03 Test disaster recovery implementation to validate the implementation](https://docs.aws.amazon.com/wellarchitected/latest/framework/rel_planning_for_recovery_dr_tested.html) — Recovery verification and architecture-review reasoning for q-1788635440123-1 and q-1788635451640-1.
- Iteration 3 · 2026-09-05 · [REL12-BP02 Perform post-incident analysis](https://docs.aws.amazon.com/wellarchitected/latest/framework/rel_testing_resiliency_rca_resiliency.html) — Contributing causes, incident evidence, and corrective actions for q-1788635461796-1.
- Iteration 3 · 2026-09-05 · [Disaster recovery options in the cloud](https://docs.aws.amazon.com/whitepapers/latest/disaster-recovery-workloads-on-aws/disaster-recovery-options-in-the-cloud.html) — Recovery strategies and usable failover interpretations for q-1788635494021-1 and q-1788635547232-1.
- Iteration 3 · 2026-09-05 · [What Is AWS CloudTrail?](https://docs.aws.amazon.com/awscloudtrail/latest/userguide/cloudtrail-user-guide.html) — AWS account activity auditing distinctions for q-1788635637393-1 and q-1788635684808-1.
- Iteration 4 · 2026-09-05 · [Evaluating modernization readiness for applications in the AWS Cloud](https://docs.aws.amazon.com/prescriptive-guidance/latest/modernization-assessing-applications/introduction.html) — Migration questions: assessment, application constraints, and target architecture readiness.
- Iteration 4 · 2026-09-05 · [Strangler fig pattern](https://docs.aws.amazon.com/prescriptive-guidance/latest/cloud-design-patterns/strangler-fig.html) — Migration questions 3 and 4: incremental modernization and rewrite trade-offs.
- Iteration 4 · 2026-09-05 · [Troubleshooting Amazon OpenSearch Service](https://docs.aws.amazon.com/opensearch-service/latest/developerguide/handling-errors.html) — Broken-search questions: symptom-driven diagnosis and conditional capacity remedies.
- Iteration 4 · 2026-09-05 · [PostgreSQL documentation: Using EXPLAIN](https://www.postgresql.org/docs/current/using-explain.html) — Slow-report question 2: query-plan inspection and execution evidence.
- Iteration 5 · 2026-09-05 · [MySQL 8.4 Reference Manual: The Slow Query Log](https://dev.mysql.com/doc/refman/8.4/en/slow-query-log.html) — q-1788635992678-1: log timing, thresholds, and diagnostic limitations.
- Iteration 5 · 2026-09-05 · [Inspecting SSL/TLS traffic with TLS inspection configurations in AWS Network Firewall](https://docs.aws.amazon.com/network-firewall/latest/developerguide/tls-inspection-configurations.html) — q-1788636151444-1: explicit configuration needed for encrypted payload inspection.
- Iteration 5 · 2026-09-05 · [CloudTrail userIdentity element](https://docs.aws.amazon.com/awscloudtrail/latest/userguide/cloudtrail-event-reference-user-identity.html) — q-1788636225320-1: AWS caller identity versus application-user attribution.
- Iteration 6 · 2026-09-05 · [Security best practices in IAM](https://docs.aws.amazon.com/IAM/latest/UserGuide/best-practices.html) — Least-privilege interpretation and authorization verification for q-1788636259098-1.
- Iteration 6 · 2026-09-05 · [Secure API access with MFA](https://docs.aws.amazon.com/IAM/latest/UserGuide/id_credentials_mfa_configure-api-require.html) — Distinguishing hardware MFA enrollment from protection of API requests for q-1788636337780-1.
- Iteration 6 · 2026-09-05 · [Disaster recovery options in the cloud](https://docs.aws.amazon.com/whitepapers/latest/disaster-recovery-workloads-on-aws/disaster-recovery-options-in-the-cloud.html) — Pilot light, warm standby, and active-active tradeoffs for q-1788636357111-1 and q-1788636405182-1.
- Iteration 6 · 2026-09-05 · [Process Amazon S3 event notifications with Lambda](https://docs.aws.amazon.com/lambda/latest/dg/with-s3.html) — Asynchronous processing, permissions, and recursive-trigger considerations for q-1788636513589-1.
- Iteration 6 · 2026-09-05 · [Leadership Principles](https://www.amazon.jobs/content/en/our-workplace/leadership-principles) — Ownership and collaboration interpretation for q-1788636441177-1; current 16-principle context for the separately retained historical poster.
- Iteration 7 · 2026-09-05 · [REL13-BP01 Define recovery objectives for downtime and data loss](https://docs.aws.amazon.com/wellarchitected/latest/reliability-pillar/rel_planning_for_recovery_objective_defined_recovery.html) — Definitions and independent evaluation of RTO and RPO across the five recovery rating questions.
- Iteration 7 · 2026-09-05 · [RFC 9110: HTTP Semantics](https://www.rfc-editor.org/rfc/rfc9110.html) — POST-to-GET redirect behavior and method-preserving redirects in q-1788636779078-2.
- Iteration 7 · 2026-09-05 · [Restoring to a DB instance](https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_RestoreFromSnapshot.html) — Replacement-instance snapshot restoration and rollback qualifications in q-1788636939776-1.
- Iteration 8 · 2026-09-05 · [REL13-BP01 Define recovery objectives for downtime and data loss](https://docs.aws.amazon.com/wellarchitected/latest/reliability-pillar/rel_planning_for_recovery_objective_defined_recovery.html) — Business recovery requirements and dependency analysis for backup planning and the cropped active-active question.
- Iteration 8 · 2026-09-05 · [PostgreSQL: Log-Shipping Standby Servers](https://www.postgresql.org/docs/current/warm-standby.html) — Synchronous acknowledgement latency and asynchronous data-loss windows in the zero-RPO question.
- Iteration 8 · 2026-09-05 · [Decompose by business capability](https://docs.aws.amazon.com/prescriptive-guidance/latest/modernization-decomposing-monoliths/decompose-business-capability.html) — Requirements discovery, business capability boundaries and independent service deployment.
- Iteration 9 · 2026-09-05 · [Understand cache policies](https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/cache-key-understand-cache-policy.html) — CloudFront cache-key settings, TTL overrides and disabling caching.
- Iteration 9 · 2026-09-05 · [How Amazon Route 53 chooses records when health checking is configured](https://docs.aws.amazon.com/Route53/latest/DeveloperGuide/health-checks-how-route-53-chooses-records.html) — Health-based record selection and all-unhealthy fallback.
- Iteration 9 · 2026-09-05 · [Regional NAT gateways for automatic multi-AZ expansion](https://docs.aws.amazon.com/vpc/latest/userguide/nat-gateways-regional.html) — Regional versus zonal NAT, expansion delay and private-connectivity limitations.
- Iteration 9 · 2026-09-05 · [Fetch Standard: HTTP-redirect fetch](https://fetch.spec.whatwg.org/#http-redirect-fetch) — Browser POST-to-GET redirect behavior for q-1788636779078-2.
- Iteration 10 · 2026-09-06 · [Health checks for Application Load Balancer target groups](https://docs.aws.amazon.com/elasticloadbalancing/latest/application/target-group-health-checks.html) — ALB health states, initial checks, response matching and all-unhealthy fail-open behavior in load-balancer-target-health.
- Iteration 10 · 2026-09-06 · [RFC 8725: JSON Web Token Best Current Practices](https://www.rfc-editor.org/rfc/rfc8725.html) — JWT algorithm, trusted-key, issuer, audience and token-substitution controls in durable-sessions-authentication.
- Iteration 10 · 2026-09-06 · [Target tracking scaling policies for Amazon EC2 Auto Scaling](https://docs.aws.amazon.com/autoscaling/ec2/userguide/as-scaling-target-tracking.html) — Proportional scaling metrics, managed alarms and normalized queue backlog in ec2-scaling-capacity.
- Iteration 10 · 2026-09-06 · [Amazon S3 Event Notifications](https://docs.aws.amazon.com/AmazonS3/latest/userguide/EventNotifications.html) — Asynchronous notifications, duplicate processing and image-readiness constraints in compute-deployment-modernization.
- Iteration 10 · 2026-09-06 · [How EC2 Image Builder works](https://docs.aws.amazon.com/imagebuilder/latest/userguide/how-image-builder-works.html) — Recipes, build/test components, infrastructure and distribution in fast-startup-golden-images.
- Iteration 11 · 2026-09-06 · [REL13-BP01 Define recovery objectives for downtime and data loss](https://docs.aws.amazon.com/wellarchitected/latest/reliability-pillar/rel_planning_for_recovery_objective_defined_recovery.html) — Business-derived recovery objectives and dependency-compatible recovery budgets.
- Iteration 11 · 2026-09-06 · [Disaster recovery options in the cloud](https://docs.aws.amazon.com/whitepapers/latest/disaster-recovery-workloads-on-aws/disaster-recovery-options-in-the-cloud.html) — Backup/restore, pilot light, warm standby, hot standby and active-active readiness distinctions.
- Iteration 11 · 2026-09-06 · [PostgreSQL: Write Ahead Log](https://www.postgresql.org/docs/current/runtime-config-wal.html) — Remote write, durable flush and replay acknowledgement semantics.
- Iteration 11 · 2026-09-06 · [Using DynamoDB global tables](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/bp-global-table-design.html) — MREC/MRSC distinctions, zero RPO, topology, witness and feature constraints.
- Iteration 11 · 2026-09-06 · [Restore testing validation](https://docs.aws.amazon.com/aws-backup/latest/devguide/restore-testing-validation.html) — Application validation beyond successful restore-job completion.
- Iteration 12 · 2026-09-06 · [Working with CloudTrail event history](https://docs.aws.amazon.com/awscloudtrail/latest/userguide/view-cloudtrail-events.html) — Regional management-event history, retention window and data-event exclusions in audit-log-pipelines.
- Iteration 12 · 2026-09-06 · [Real-time processing of log data with subscriptions](https://docs.aws.amazon.com/AmazonCloudWatch/latest/logs/Subscriptions.html) — Subscription destinations, duplicate delivery, bounded retries and delivery gaps.
- Iteration 12 · 2026-09-06 · [OPS10-BP05 Define a customer communication plan for service-impacting events](https://docs.aws.amazon.com/wellarchitected/latest/operational-excellence-pillar/ops_event_response_push_notify.html) — Communication ownership, resilient channels and timely customer updates.
- Iteration 12 · 2026-09-06 · [PSI - Pressure Stall Information](https://docs.kernel.org/accounting/psi.html) — Linux resource stalls and distinguishing active pressure from allocated swap.
- Iteration 13 · 2026-09-06 · [Oversize web request components in AWS WAF](https://docs.aws.amazon.com/waf/latest/developerguide/waf-oversize-request-components.html) — Application-security chapter: body inspection limits and oversize handling.
- Iteration 13 · 2026-09-06 · [IAM policy evaluation logic](https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_evaluation-logic.html) — IAM chapter: request context, grants and explicit denies.
- Iteration 13 · 2026-09-06 · [Revoke IAM role temporary security credentials](https://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles_use_revoke-sessions.html) — Credentials chapter: issuance cutoffs, existing sessions and reissuance risks.
- Iteration 13 · 2026-09-06 · [Rotate AWS KMS keys](https://docs.aws.amazon.com/kms/latest/developerguide/rotate-keys.html) — Encryption chapter: rotation eligibility, retained decryptability and absence of automatic data re-encryption.
- Iteration 14 · 2026-09-06 · [How to perform a major version upgrade for RDS for PostgreSQL](https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_UpgradeDBInstance.PostgreSQL.MajorVersion.Process.html) — Representative upgrade rehearsal, parameter compatibility, backups and query-plan regressions.
- Iteration 14 · 2026-09-06 · [Using DynamoDB global tables](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/bp-global-table-design.html) — MREC/MRSC consistency, topology and unsupported TTL, transactions and local secondary indexes.
- Iteration 14 · 2026-09-06 · [Durability in ElastiCache](https://docs.aws.amazon.com/AmazonElastiCache/latest/dg/durability.html) — Multi-AZ transactional logging and synchronous versus asynchronous acknowledgement guarantees.
- Iteration 14 · 2026-09-06 · [Amazon EBS I/O characteristics and monitoring](https://docs.aws.amazon.com/ebs/latest/userguide/ebs-io-characteristics.html) — IOPS, operation size, throughput, queueing and performance constraints.
- Iteration 14 · 2026-09-06 · [Understanding archive retrieval options](https://docs.aws.amazon.com/AmazonS3/latest/userguide/restoring-objects-retrieval-options.html) — Archive retrieval timing and the two-hour end-to-end restore calculation.
- Iteration 14 · 2026-09-06 · [Features of Amazon EFS](https://docs.aws.amazon.com/efs/latest/ug/features.html) — NFS consistency, advisory locking, Regional versus One Zone failure domains and Archive restrictions.
- Iteration 15 · 2026-09-06 · [Shared Responsibility Model](https://aws.amazon.com/compliance/shared-responsibility-model/) — Guest operating-system ownership and customer data and permissions responsibilities.
- Iteration 15 · 2026-09-06 · [Creating tasks for ongoing replication using AWS DMS](https://docs.aws.amazon.com/dms/latest/userguide/CHAP_Task.CDC.html) — Log-based change capture, variable replication latency and migration convergence.
- Iteration 15 · 2026-09-06 · [Exactly-once processing in Amazon SQS](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/FIFO-queues-exactly-once-processing.html) — Five-minute FIFO producer deduplication scope and its distinction from atomic business effects.
- Iteration 15 · 2026-09-06 · [REL13-BP01 Define recovery objectives for downtime and data loss](https://docs.aws.amazon.com/wellarchitected/latest/reliability-pillar/rel_planning_for_recovery_objective_defined_recovery.html) — Recovery objectives across dependent workloads and the application-tier recovery question.
- Iteration 15 · 2026-09-06 · [Evaluate exit strategy requirements](https://docs.aws.amazon.com/prescriptive-guidance/latest/strategy-multicloud-fsi/exit-strategy.html) — Distinguishing planned provider exit from unexpected-outage recovery.
- Iteration 15 · 2026-09-06 · [Workload Identity Federation](https://docs.cloud.google.com/iam/docs/workload-identity-federation) — Cross-cloud workload identity, external identity mapping and avoiding permanent service-account keys.
- Iteration 16 · 2026-09-06 · [OPS01-BP01 Evaluate external customer needs](https://docs.aws.amazon.com/wellarchitected/latest/framework/ops_priorities_ext_cust_needs.html) — Stakeholder discovery and measurable customer outcomes in customer-discovery-accountable-decisions.
- Iteration 16 · 2026-09-06 · [Understanding how Savings Plans apply to your usage](https://docs.aws.amazon.com/savingsplans/latest/userguide/sp-applying.html) — Hourly commitment utilization and unused commitment constraints in cost-engineering-finops-tco.
- Iteration 16 · 2026-09-06 · [Monitor network performance for ENA settings on your EC2 instance](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/monitoring-network-performance-ena.html) — Bandwidth, packet-rate, and connection-tracking diagnostics in performance-capacity-test-plans.
- Iteration 16 · 2026-09-06 · [OpenAPI Specification v3.1.1](https://spec.openapis.org/oas/v3.1.1.html) — Versioned API descriptions and contract verification in technical-writing-documentation-engineering.
- Iteration 16 · 2026-09-06 · [What to look for in a code review — Google Engineering Practices](https://google.github.io/eng-practices/review/reviewer/looking-for.html) — Documentation review alongside behavior changes and prevention of documentation drift.
- Iteration 17 · 2026-09-06 · [Leadership Principles](https://www.amazon.jobs/content/en/our-workplace/leadership-principles) — Verified current names, brief paraphrased definitions, the 16-principle inventory, and links to eight official explanatory transcripts.
- Iteration 17 · 2026-09-06 · [Amazon announces two new Leadership Principles](https://www.aboutamazon.com/news/company-news/two-new-leadership-principles) — Explained the historical change from 14 to 16 principles and identified the two additions.
- Iteration 17 · 2026-09-06 · [Interview preparation for data roles](https://amazon.jobs/content/en/how-we-hire/university/data) — Supported STAR structure and preparation grounded in actual past behavior without generalizing role-specific interview schedules.
- Iteration 17 · 2026-09-06 · [OPS05-BP01 Use version control](https://docs.aws.amazon.com/wellarchitected/latest/operational-excellence-pillar/ops_dev_integ_version_control.html) — Supported tracking versions of code and operational assets in Ownership and Highest Standards documentation exercises.
- Iteration 18 · 2026-09-06 · [Leadership Principles](https://www.amazon.jobs/content/en/our-workplace/leadership-principles) — Verified current names, brief definition paraphrases and that Have Backbone; Disagree and Commit is one principle.
- Iteration 18 · 2026-09-06 · [Amazon announces two new Leadership Principles](https://www.aboutamazon.com/news/company-news/two-new-leadership-principles) — Explained the two additions distinguishing the historical 14-principle poster from the current 16.
- Iteration 18 · 2026-09-06 · [Interview Loop](https://amazon.jobs/content/en/how-we-hire/interview-loop) — Official behavioral-question and STAR preparation context for the original evidence workshops.
- Iteration 19 · 2026-09-06 · [Using DynamoDB global tables](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/bp-global-table-design.html) — MREC versus MRSC consistency, replication, topology, and feature restrictions.
- Iteration 19 · 2026-09-06 · [Durability options — Amazon ElastiCache](https://docs.aws.amazon.com/AmazonElastiCache/latest/dg/Durability.Options.html) — Synchronous versus asynchronous acknowledgement, potential data loss, and eviction distinctions.
- Iteration 19 · 2026-09-06 · [RFC 9110: HTTP Semantics](https://www.rfc-editor.org/rfc/rfc9110.html) — HTTP methods, idempotency, redirects, and POST-to-GET quiz terminology.
- Iteration 19 · 2026-09-06 · [Leadership Principles](https://www.amazon.jobs/content/en/our-workplace/leadership-principles) — Current principle terminology and behavioral reflection without fabricated answer keys.
- Iteration 20 · 2026-09-06 · [Durability options — Amazon ElastiCache](https://docs.aws.amazon.com/AmazonElastiCache/latest/dg/Durability.Options.html) — Correct session-store durability, acknowledgement and eviction guidance.
- Iteration 20 · 2026-09-06 · [Best practices for designing and architecting with DynamoDB global tables](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/bp-global-table-design.html) — Scope TTL examples and distinguish MRSC constraints and replicated logical corruption.
- Iteration 20 · 2026-09-06 · [Amazon SNS message archiving, replay, and analytics](https://docs.aws.amazon.com/sns/latest/dg/message-archiving-and-analytics.html) — Correct standard-versus-FIFO archive and replay distinctions.
- Iteration 20 · 2026-09-06 · [Leadership Principles — Amazon Jobs](https://www.amazon.jobs/content/en/our-workplace/leadership-principles) — Verify all 16 current principle names and retain the historical poster distinction.
- Iteration 20 · 2026-09-06 · [Histograms and summaries — Prometheus](https://prometheus.io/docs/practices/histograms/) — Correct percentile aggregation guidance and add an equal-population counterexample.
- Iteration 20 · 2026-09-06 · [AWS Systems Manager Run Command](https://docs.aws.amazon.com/systems-manager/latest/userguide/run-command.html) — Expand remote-installation mechanics, execution status and readiness reasoning.