I've tried to add an index on records.status, but the cardinality is so low (<5 unique values) a seq scan was still used.

The query:

select distinct "events".* from "events" 
inner join (select "records".* from "records" where "status" = 'Mined') as "record" on "record"."guid" = CAST("events"."return_values"#>>'{guid}' AS text) 
where "events"."status" = 'Waiting' and "event" in ('RecordUpdated', 'RecordDiscovery', 'RecordRetrieval') 
order by "block_number" asc, "transaction_index" asc, "transaction_hash" asc, "log_index" asc 
limit 100;

The execution plan looks like:

 Limit  (cost=122673.00..122677.25 rows=100 width=1639) (actual time=575.631..575.632 rows=0 loops=1)
   ->  Unique  (cost=122673.00..124045.11 rows=32285 width=1639) (actual time=548.071..548.071 rows=0 loops=1)
         ->  Sort  (cost=122673.00..122753.71 rows=32285 width=1639) (actual time=548.068..548.069 rows=0 loops=1)
               Sort Key: events.block_number, events.transaction_index, events.transaction_hash, events.log_index, events.event_id, events.block_hash, events.address, events.return_values, events.event, events.signature, events.raw, events.processing_error, events.confirmations, events.created_at, events.updated_at, events.id
               Sort Method: quicksort  Memory: 25kB
               ->  Gather  (cost=47192.22..97302.09 rows=32285 width=1639) (actual time=548.048..571.664 rows=0 loops=1)
                     Workers Planned: 2
                     Workers Launched: 2
                     ->  Parallel Hash Join  (cost=46192.22..93073.59 rows=13452 width=1639) (actual time=526.239..526.241 rows=0 loops=3)
                           Hash Cond: ((events.return_values #>> '{guid}'::text[]) = (records.guid)::text)
                           ->  Parallel Index Scan using events_status_index on events  (cost=0.43..46843.84 rows=13804 width=1639) (actual time=0.106..36.976 rows=16870 loops=3)
                                 Index Cond: (status = 'Waiting'::event_status)
                                 Filter: ((event)::text = ANY ('{RecordUpdated,RecordDiscovery,RecordRetrieval}'::text[]))
                                 Rows Removed by Filter: 1
                           ->  Parallel Hash  (cost=42957.65..42957.65 rows=258731 width=44) (actual time=462.763..462.764 rows=205834 loops=3)
                                 Buckets: 1048576  Batches: 1  Memory Usage: 56672kB
                                 ->  Parallel Seq Scan on records  (cost=0.00..42957.65 rows=258731 width=44) (actual time=16.322..244.807 rows=205834 loops=3)
                                       Filter: (status = 'Mined'::record_status)
                                       Rows Removed by Filter: 6625
 Planning Time: 0.432 ms
 JIT:
   Functions: 50
   Options: Inlining false, Optimization false, Expressions true, Deforming true
   Timing: Generation 8.788 ms, Inlining 0.000 ms, Optimization 3.711 ms, Emission 71.684 ms, Total 84.183 ms
 Execution Time: 602.684 ms
(25 rows)

events table:

                                          Table "public.events"
      Column       |           Type           | Collation | Nullable |              Default
-------------------+--------------------------+-----------+----------+------------------------------------
 event_id          | character varying(255)   |           | not null |
 log_index         | integer                  |           | not null |
 transaction_index | integer                  |           | not null |
 transaction_hash  | character varying(255)   |           | not null |
 block_hash        | character varying(255)   |           | not null |
 block_number      | integer                  |           | not null |
 address           | character varying(255)   |           | not null |
 return_values     | jsonb                    |           | not null |
 event             | character varying(255)   |           | not null |
 signature         | character varying(255)   |           | not null |
 raw               | jsonb                    |           | not null |
 status            | event_status             |           | not null |
 processing_error  | character varying(255)   |           |          |
 confirmations     | integer                  |           | not null |
 created_at        | timestamp with time zone |           |          |
 updated_at        | timestamp with time zone |           |          |
 id                | integer                  |           | not null | nextval('events_id_seq'::regclass)
Indexes:
    "events_pkey" PRIMARY KEY, btree (id)
    "events_block_log" btree (block_number, log_index)
    "events_status_index" btree (status)

records table:

                            Table "public.records"
      Column      |           Type           | Collation | Nullable | Default
------------------+--------------------------+-----------+----------+---------
 guid             | character varying(255)   |           | not null |
 data_hash        | character varying(255)   |           | not null |
 transaction_hash | character varying(255)   |           | not null |
 url              | character varying(255)   |           | not null |
 status           | record_status            |           | not null |
 created_at       | timestamp with time zone |           |          |
 updated_at       | timestamp with time zone |           |          |
 client_id        | character varying(64)    |           | not null |
 event_id         | character varying(255)   |           |          |
 user_id          | character varying(255)   |           |          |
Indexes:
    "records_pkey" PRIMARY KEY, btree (guid)
    "records_client_id_index" btree (client_id)
    "records_event_id_index" btree (event_id)
    "records_user_id_index" btree (user_id)
Foreign-key constraints:
    "records_client_id_foreign" FOREIGN KEY (client_id) REFERENCES clients(id) ON DELETE CASCADE
Referenced by:
    TABLE "discoveries" CONSTRAINT "discoveries_record_guid_foreign" FOREIGN KEY (record_guid) REFERENCES records(guid) ON DELETE CASCADE
    TABLE "record_dependencies" CONSTRAINT "record_dependencies_record_foreign" FOREIGN KEY (record) REFERENCES records(guid) ON DELETE CASCADE
    TABLE "retrievals" CONSTRAINT "retrievals_record_guid_foreign" FOREIGN KEY (record_guid) REFERENCES records(guid) ON DELETE CASCADE

Any tips would be greatly appreciated