Different .kibana_* indices After upgrading

Upgrade ELK stack from 7.13 to 7.15
I checked /_cat/indices/.kibana?v*

health status index                           uuid                   pri rep docs.count docs.deleted store.size pri.store.size
green  open   .kibana-event-log-7.15.2-000001 6TDXTgf8RwGjVH3LMJcOCA   1   1         57            0    195.2kb         97.5kb
green  open   .kibana-event-log-7.12.0-000004 jCatWqqqRJmUplxQ1hgD9w   1   1          0            0       416b           208b
green  open   .kibana-event-log-7.12.0-000005 U76-rUAARaGC_DfcCpRu6Q   1   1          0            0       416b           208b
green  open   .kibana_security_session_1      IAslrfK5Sc6AcFbAoyu_3g   1   1          1            0       11kb          5.5kb
green  open   .kibana-event-log-7.12.0-000006 amxJywUMSPib_-J0ExE6nA   1   1          0            0       416b           208b
green  open   .kibana_7.12.0_001              o5xRcvxgSsSztBNOCfIkJA   1   1        889           76      5.6mb          2.8mb
green  open   .kibana-event-log-7.12.0-000003 tqJa5UroT_qVl3yQuyAIEg   1   1          0            0       416b           208b
green  open   .kibana_task_manager_7.15.2_001 DGlfNTB8RIWdGErmzWWVfg   1   1         34         1994    733.9kb        331.7kb
green  open   .kibana_7.13.2_001              MBCEN4KvSrW4WUmNXLAvHw   1   1       1841          490      8.3mb            4mb
green  open   .kibana-event-log-7.13.2-000002 9AzRupr4RRSOHvGQI2ESWA   1   1   11555241            0      1.3gb        671.2mb
green  open   .kibana-event-log-7.13.2-000003 j-1akr2xRpCcMevd4DTi6A   1   1   12541998            0      1.4gb        720.2mb
green  open   .kibana-event-log-7.13.2-000004 4nUblHNZTuW09FrpyhIBoA   1   1    1031364            0    130.3mb         65.1mb
green  open   .kibana-event-log-7.13.2-000005 cgOKFRa5SAWYXoGPfv8Eaw   1   1     702537            0     86.7mb         43.4mb
green  open   .kibana_task_manager_7.13.2_001 TByrB3fUSTSfQnf1v5aGpQ   1   1         29         2144    650.1kb        381.1kb
green  open   .kibana_7.15.2_001              D2FpFf09Skq0Ww6rxvp6Bg   1   1       1848         2766     19.5mb          9.7mb

which .kibana index i can delete safely without intrupting and dashboards or it can be deleted automatically.

Hi @Aniket_Pant ,

you can have a look at this page to know more about kibana indices, why there are kept and it which case you can delete them safely: Upgrade migrations | Kibana Guide [7.15] | Elastic (and all the sections above for a more in-depth information).

alias                       index                           filter routing.index routing.search is_write_index
.kibana                     .kibana_7.15.2_001              -      -             -              -
.kibana_7.15.2              .kibana_7.15.2_001              -      -             -              -
.kibana-event-log-7.15.2    .kibana-event-log-7.15.2-000001 -      -             -              true
.kibana-event-log-7.12.0    .kibana-event-log-7.12.0-000003 -      -             -              false
.kibana-event-log-7.12.0    .kibana-event-log-7.12.0-000004 -      -             -              false
.kibana-event-log-7.13.2    .kibana-event-log-7.13.2-000002 -      -             -              false
.kibana_task_manager_7.13.2 .kibana_task_manager_7.13.2_001 -      -             -              -
.kibana-event-log-7.13.2    .kibana-event-log-7.13.2-000004 -      -             -              false
.kibana_7.13.2              .kibana_7.13.2_001              -      -             -              -
.kibana-event-log-7.13.2    .kibana-event-log-7.13.2-000003 -      -             -              false
.kibana-event-log-7.13.2    .kibana-event-log-7.13.2-000005 -      -             -              true
.kibana-event-log-7.12.0    .kibana-event-log-7.12.0-000005 -      -             -              false
.kibana_task_manager        .kibana_task_manager_7.15.2_001 -      -             -              -
.kibana_task_manager_7.15.2 .kibana_task_manager_7.15.2_001 -      -             -              -
.kibana-event-log-7.12.0    .kibana-event-log-7.12.0-000006 -      -             -              true

Handling old .kibana_N indices

Kibana only uses the index that the .kibana and .kibana_task_manager alias points to.

in my case .kibana ,.kibana_7.15.2 alias is pointing to .kibana_7.15.2_001 and .kibana_7.15.2_001 respectively but their is_write_index is -

.kibana_task_manager , .kibana_task_manager_7.15.2 is pointing to .kibana_task_manager_7.15.2_001 their also is_write_index is -

can i delete it .kibana_7.13.2 index .kibana_event-log-7.13.2 index and
.kibana-event-log-7.12.0

@Marco_Liberati can users just delete older versions of indices completely.
eg if they are on 7.15, anything with a version number lower than than in the name can just be removed?