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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '673a13cac712bdb83ba5afbb7be66e3e5523c99faeea645266c61f02eb9c081f' 
  AND token = 'Mqpnn9wroxJb6LSFfBuXS/MhzW9J9b16OCTgXntLdCM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}