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Architecture Evolution Path

Self-Hosted Infrastructure → Managed Cloud Services

Medium

Replacing self-hosted PostgreSQL, Redis, and Kafka with managed equivalents (RDS, ElastiCache, MSK) to eliminate infrastructure maintenance overhead: automated backups, managed failover, and compliance certifications: at the cost of reduced configuration control, vendor lock-in, and higher cost at very large scale.

Topology Changes

Architecture Diff
-2 removed2 modified
Self-Hosted PostgreSQL + Redis + Kafka4 changes
→
RDS + ElastiCache + MSK (or equivalent)2 changes
Unchanged
Added
Removed
Modified

From

Self-Hosted PostgreSQL + Redis + Kafka

→
4 mutations

To

RDS + ElastiCache + MSK (or equivalent)

Topology Mutations

Technology ReplacedPostgreSQL → RDS PostgreSQL

Self-hosted PostgreSQL primary (and manual replica) is replaced by an RDS Multi-AZ instance. RDS provides automated backups (point-in-time recovery up to 35 days), automatic minor version patching, and Multi-AZ failover with < 60 seconds promotion time.

Operational Impact

RDS adds approximately 1–2ms additional network latency compared to a co-located self-hosted instance. Some PostgreSQL extensions are unavailable (e.g., PostGIS is supported; custom C extensions are not).

Component RemovedSelf-Hosted Replication Management Tooling

Custom Patroni/repmgr configuration, manual failover scripts, and self-managed WAL archival are replaced by RDS Multi-AZ automated management. The operational runbooks for replica promotion and replication repair are no longer relevant.

Operational Impact

Engineers lose fine-grained control over replication configuration and failover timing. RDS failover is automatic: a malfunctioning primary will be replaced without human approval.

Technology ReplacedRedis → ElastiCache Redis

Self-hosted Redis cluster is replaced by ElastiCache Redis with automated failover. Cluster mode optional: enables horizontal sharding of cache data across multiple shards.

Operational Impact

ElastiCache does not support all Redis commands in cluster mode (KEYS, MGET across slots). Applications using these commands must be refactored before migrating to cluster mode.

Component RemovedSelf-Hosted Kafka Cluster Management

ZooKeeper-managed or KRaft Kafka cluster replaced by Amazon MSK. MSK handles broker provisioning, ZooKeeper management (or KRaft migration), automated storage scaling, and certificate rotation.

Operational Impact

MSK does not expose all Kafka configuration parameters: some advanced broker settings (log.message.downconversion.enable, certain security plugin configurations) are unavailable.

Migration Stages

1
Provision Managed Services and Validate Connectivity1 week

Provision RDS, ElastiCache, and MSK instances in target configuration. Run connectivity and performance benchmarks from the application's network location: measure connection latency, throughput, and whether any required features are unavailable on the managed service. Identify and resolve feature gaps before committing to migration.

Low risk·Rollback possible
2
Database Migration: Replica to RDS1–2 weeks

Use AWS DMS or pg_dump/pg_restore to seed the RDS instance from the self-hosted primary. For live migration with minimal downtime, configure logical replication from self-hosted PostgreSQL to RDS. Validate row counts, constraints, and index parity. Test application connection to RDS in a staging environment.

Medium risk·Rollback possible
3
Database Cutover (Maintenance Window)2–4 hours active window

During a planned maintenance window: stop application writes, allow replication to fully catch up (zero lag), update application connection strings to RDS endpoint, restart application, validate writes and reads. Total downtime target: 5–15 minutes. Keep self-hosted instance available but read-only for 48 hours as rollback option.

High risk·Rollback possible
4
Redis and Kafka Cutover1–2 weeks

Migrate Redis: deploy application pointing to ElastiCache. Cache is stateless: application will experience a cold cache period until ElastiCache warms up. Monitor cache hit rate. Migrate Kafka: create matching topics on MSK, configure producers to dual-publish to both clusters, migrate consumers to MSK one consumer group at a time, then cut producers.

Medium risk·Rollback possible
5
Validate and Decommission Self-Hosted2–3 weeks

Run managed services in production for 2 weeks. Validate performance parity, backup restoration procedures, and failover behavior (test RDS failover in staging). After validation, decommission self-hosted instances. Update runbooks to reflect managed service operational model.

Low risk·No rollback after this stage

Migration Risks

operationalWarning

Managed services do not support all PostgreSQL extensions or Kafka broker configurations. Feature gaps discovered after migration cutover require either accepting limitations or migrating back: both are costly.

Mitigation

Audit all used PostgreSQL extensions (\\dx in psql) and Kafka configuration parameters against managed service documentation before beginning migration. Prototype any borderline features in the managed service before committing to migration timeline.

operationalWarning

Network path changes between self-hosted and managed service can increase connection latency from <1ms (same-host or same-rack) to 1–5ms (cross-AZ or managed service endpoint). Applications with N+1 query patterns may experience measurable latency regression.

Mitigation

Benchmark managed service connection latency from production application servers before migration. Identify and fix N+1 query patterns if latency increase is measurable. Place RDS in the same AZ as the primary application tier to minimize network hops.

operationalWarning

Managed service maintenance windows apply patches automatically. If the maintenance window is not set correctly, automated minor version upgrades or configuration changes may occur during business hours, causing brief connectivity disruptions.

Mitigation

Configure maintenance windows for low-traffic periods (e.g., 2–4 AM in primary user timezone). Subscribe to managed service maintenance notifications. Test application behavior during RDS Multi-AZ failover: the application must handle a brief connection drop.

Coupling Changes

operational couplingDecreases

Infrastructure maintenance responsibility is transferred to the managed service provider

Consequence

Engineering team can focus on application reliability rather than infrastructure reliability

vendor couplingIncreases

Application is now dependent on cloud provider APIs, configuration models, and service-specific behaviors

Consequence

Migrating away from managed services in the future requires rebuilding the operational model from scratch

Consistency Model Changes

  • ·Database consistency model is unchanged: RDS PostgreSQL preserves all ACID guarantees of self-hosted PostgreSQL
  • ·RDS Multi-AZ uses synchronous replication within the AZ pair: failover does not lose committed transactions
  • ·ElastiCache Redis Cluster mode introduces slot-based key distribution: cross-slot operations (MGET, transactions across keys) are unavailable

Rollback Risks

  • ·Reverting from RDS to self-hosted requires provisioning and seeding a new self-hosted instance: downtime proportional to data volume
  • ·If self-hosted infrastructure has been decommissioned, rollback requires spinning up new self-hosted instances from managed service backup exports
  • ·Configuration knowledge for self-hosted Kafka and PostgreSQL may have atrophied in the team: rollback operational complexity is higher than initial migration