Re: Proposal: Recent mutated table tracking in memory

Doing another ping - sorry for that, it's been 20 days.

Would appreciate any feedback. thank you

On Wed, Jan 14, 2026 at 10:55 AM Nadav Shatz <nadav(at)tailorbrands(dot)com> wrote:

> Hi all,
>
> Any comments or concerns? can we merge it if not?
>
> On Tue, Jan 6, 2026 at 1:25 PM Nadav Shatz <nadav(at)tailorbrands(dot)com> wrote:
>
>> Hello,
>>
>> As initially proposed under "Proposal: recent access based routing for
>> primary-replica setups" and then broken into separate tasks - i am adding
>> here a patch to implement tracking of latest mutated table, and then using
>> the replication lag as a base - deciding where to point queries when query
>> load balancing and parsing is enabled.
>>
>> More details as in the patch:
>> Feature: add in-memory table tracking to prevent stale reads from replicas
>>
>> Implement "memory map" feature that tracks recently-written database
>> tables in shared memory to prevent stale reads during replication lag.
>> When a write (INSERT/UPDATE/DELETE) occurs on a table, that table is
>> marked as "dirty" for a configurable TTL period. Any SELECT on a dirty
>> table within the TTL window is routed to primary instead of replica.
>>
>> Key features:
>> - Shared memory hash table for tracking table mutations with TTL
>> - Query parse cache with LRU eviction for performance
>> - Cold start protection (routes all queries to primary initially)
>> - Automatic TTL calculation: replication_delay × configurable factor
>> - Per-table staleness tracking with microsecond precision
>>
>> New configuration parameters:
>> - memory_map_enabled: Enable/disable the feature (default: off)
>> - memory_map_ttl_factor: TTL multiplier for replication delay (default:
>> 5.0)
>> - memory_map_cold_start_duration: Cold start period in ms (default: 2000)
>> - memory_map_table_buckets: Hash buckets for table map (default: 1024)
>> - memory_map_table_size: Max tracked tables (default: 2048)
>> - memory_map_query_buckets: Hash buckets for query cache (default: 2048)
>> - memory_map_query_cache_size: Max cached queries (default: 10000)
>>
>> Patch applies properly and tests pass.
>>
>> Open to all feedback - thank you!
>>
>> --
>> Nadav Shatz
>> Tailor Brands | CTO
>>
>
>
> --
> Nadav Shatz
> Tailor Brands | CTO
>

--
Nadav Shatz
Tailor Brands | CTO