Compare Scenarios

Migration Step 1

Both scenarios define a migration step at this stage. Social Feed Platform: triggered by 'PostgreSQL timeline read query p99 > 500ms; query plan for "'. Geospatial Tracking Platform: triggered by 'PostGIS proximity query p99 > 100ms under concurrent fleet t'.

Migration Step 2

Both scenarios define a migration step at this stage. Social Feed Platform: triggered by 'Fan-out worker queue lag during celebrity post events > 5 mi'. Geospatial Tracking Platform: triggered by 'Location update API p99 > 200ms correlated with geofence cou'.

Migration Step 3

Both scenarios define a migration step at this stage. Social Feed Platform: triggered by 'Redis memory utilization approaching 80% of a single node; R'. Geospatial Tracking Platform: triggered by 'PostgreSQL location_history table exceeding 100GB with query'.

Kafka consumer group lag for fan-out worker group growing steadily; feed propagation latency (time from post write to follower feed update) exceeding 30s p95; Redis write rate on feed keys elevated but not saturated; post activity rate normal

Tier 1: Fan-Out Worker Queue Backlog: Fan-out worker pool undersized for burst post activity or a celebrity post creating a sustained high-fan-out event. Recommended evolution: Add fan-out worker replicas; implement fan-out cost routing: route high-follower-count fan-out events to a dedicated high-cost worker pool with separate Kafka consumer group and Redis write quota; use follower count threshold (e.g., >50k followers) as the routing decision. Monitor fan-out cost per post as a first-class metric. .

Redis memory utilization > 75%; eviction rate rising; cache miss rate on feed reads increasing; cold feed read fallback queries appearing in PostgreSQL slow query log; feed read p99 > 100ms despite Redis being online

Tier 2: Redis Feed Memory Ceiling: Redis feed list storage approaching memory limit; feed items being evicted before TTL; or feed list cap set too high for available memory. Recommended evolution: Reduce feed list cap from current value toward 100–150 items; increase Redis cluster capacity or shard feed keys by user_id range across multiple Redis primaries; implement tiered feed storage: hot recent items in Redis, older items fetched from PostgreSQL on demand with explicit product UX affordance .

Redis used_memory > 75% of maxmemory; Redis evictions appearing in INFO stats; GEOSEARCH returning stale or missing entity positions; Redis OOM errors in application logs during fleet expansion events; proximity query latency increasing above 10ms baseline

Tier 1: Redis Geospatial Memory Pressure: Redis memory exhausted by unbounded geospatial entity growth without entity expiry or cleanup. Recommended evolution: Implement entity-scoped Redis key TTL tied to the last received update timestamp. Entities that have not sent a position update in > 5 minutes are expired from Redis automatically (Redis EXPIRE on the ZSET entry using a per-entity auxiliary key pattern, since ZSET members do not support per-member TTL natively). Alternatively, introduce a background reconciliation job that removes entities from the live position surface after an inactivity threshold. Shard the geospatial index across multiple Redis instances by geographic region using consistent hashing on the region key. .

TimescaleDB write p99 > 50ms; WAL volume > 200MB/minute sustained; disk I/O utilization > 80% on TimescaleDB data volume; chunk creation log entries during fleet expansion events correlated with write latency spikes; TimescaleDB worker queue depth growing during ingestion bursts

Tier 2: TimescaleDB Write Throughput Ceiling: TimescaleDB hypertable chunk write throughput saturated by high-frequency location update volume; chunk creation DDL causing write stalls during expansion. Recommended evolution: Tune TimescaleDB chunk_time_interval to match the ingestion rate: smaller chunks (1-hour intervals instead of 1-day) reduce per-chunk write volume but increase chunk creation frequency. Use timescaledb-parallel-copy for bulk historical ingestion. Move the TimescaleDB WAL to a dedicated NVMe volume. Introduce write batching at the application layer: buffer 500ms of position updates per entity and write as a single multi-row INSERT, reducing the per-update overhead from N single-row INSERTs to N/batch_size batch INSERTs. .