Optimizing query – understanding explain

I’ve got a query (partly generated by django orm, but can be modified).

For some reason, It’s very slow (between 1.5 -3 seconds, without having lots of data on the system) . I’ve got an “explain” from my newrelic trace. But I don’t really know how to read this.

Where is the query spending time?
How should I optimize the query (or add indexes to the db)

Explain plan in explain.depesz

Query:

SELECT 
    "top_traders_toptrader"."user_id",              "top_traders_toptrader"."social_profile_id", 
    "top_traders_toptrader"."execution_account_id", "top_traders_toptrader"."performance_account_id", 

    COUNT(DISTINCT "social_subscription"."subscriber_id") AS "num_subscribers", 
    COUNT(DISTINCT "social_follow"."follower_id") AS "num_followerers",
    COUNT(DISTINCT "execution_position"."isin") AS "stock_count", 

    "social_socialprofile"."user_id", "social_socialprofile"."is_hidden", 
    "social_socialprofile"."role",    "social_socialprofile"."image", 
    "social_socialprofile"."is_excluded", 

    "authUsers_user"."id",           "authUsers_user"."username", 
    "authUsers_user"."first_name",   "authUsers_user"."last_name", 
    "authUsers_user"."is_deleted",   "authUsers_user"."date_joined",
    "authUsers_user"."is_superuser", "authUsers_user"."is_demo", 

    "execution_account"."user",      "execution_account"."date_joined",
    "execution_account"."is_active",

    "performance_accountperformance"."user_id",                "performance_accountperformance"."account_id",
    "performance_accountperformance"."live_periodic_gains_id", "performance_accountperformance"."role",
    "performance_accountperformance"."field",                  "performance_periodicgain"."id", 
    "performance_periodicgain"."daily",                        "performance_periodicgain"."weekly", 
    "performance_periodicgain"."monthly",                      "performance_periodicgain"."three_monthly", 
    "performance_periodicgain"."six_monthly",                  "performance_periodicgain"."yearly" 

FROM 
        "top_traders_toptrader" 
    LEFT OUTER JOIN "execution_account" 
        ON ( "top_traders_toptrader"."execution_account_id" = "execution_account"."user" )
    INNER JOIN "performance_accountperformance" 
        ON ( "top_traders_toptrader"."performance_account_id" = "performance_accountperformance"."user_id" ) 
    LEFT OUTER JOIN "social_socialprofile" 
        ON ( "top_traders_toptrader"."social_profile_id" = "social_socialprofile"."user_id" ) 
    LEFT OUTER JOIN "social_subscription" 
        ON ( "social_socialprofile"."user_id" = "social_subscription"."subscribed_to_id" ) 
    LEFT OUTER JOIN "social_follower" 
        ON ( "social_socialprofile"."user_id" = "social_follower"."followeree_id" ) 
    LEFT OUTER JOIN "execution_position"
        ON ( "execution_account"."user" = "execution_position"."account_id" ) 
    LEFT OUTER JOIN "authUsers_user" 
        ON ( "social_socialprofile"."user_id" = "authUsers_user"."id" ) 
    LEFT OUTER JOIN "performance_periodicgain" 
        ON ( "performance_accountperformance"."live_periodic_gains_id" = "performance_periodicgain"."id" ) 
WHERE 
    (NOT ("top_traders_toptrader"."execution_account_id" IS NULL) 
     AND NOT ("top_traders_toptrader"."performance_account_id" IS NULL) 
     AND NOT ("top_traders_toptrader"."social_profile_id" IS NULL) 
     AND NOT ("social_socialprofile"."is_hidden" = True  
              AND "social_socialprofile"."is_hidden" IS NOT NULL) 
     AND "social_socialprofile"."role" = 20  
     AND NOT ((("top_traders_toptrader"."execution_account_id" IN 
                    (SELECT U1."user" 
                     FROM "execution_account" U1 
                        LEFT OUTER JOIN "execution_order" U2 
                             ON ( U1."user" = U2."account_id" ) 
                     WHERE U2."id" IS NULL) 
                AND "top_traders_toptrader"."execution_account_id" IS NOT NULL) 
               OR "top_traders_toptrader"."execution_account_id" IS NULL))) 

GROUP BY 
    "top_traders_toptrader"."user_id", 
    "top_traders_toptrader"."social_profile_id", 
    "top_traders_toptrader"."execution_account_id", 
    "top_traders_toptrader"."performance_account_id", 

    "social_socialprofile"."user_id", 
    "social_socialprofile"."is_hidden", 
    "social_socialprofile"."role", 
    "social_socialprofile"."image", 
    "social_socialprofile"."is_excluded", 

    "authUsers_user"."id", 
    "authUsers_user"."username", 
    "authUsers_user"."first_name", 
    "authUsers_user"."last_name", 
    "authUsers_user"."is_deleted", 
    "authUsers_user"."date_joined", 
    "authUsers_user"."is_superuser", 
    "authUsers_user"."is_demo", 

    "execution_account"."user", 
    "execution_account"."date_joined", 
    "execution_account"."is_active", 

    "performance_accountperformance"."user_id",
    "performance_accountperformance"."account_id", 
    "performance_accountperformance"."live_periodic_gains_id", 
    "performance_accountperformance"."role", 
    "performance_accountperformance"."field", 

    "performance_periodicgain"."id", 
    "performance_periodicgain"."daily", 
    "performance_periodicgain"."weekly",
    "performance_periodicgain"."monthly", 
    "performance_periodicgain"."three_monthly", 
    "performance_periodicgain"."six_monthly",
    "performance_periodicgain"."yearly" 

ORDER BY 
    "num_subscribers" DESC ;