SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b9f399be170bafee08fc0a7dfa0658970991223e58362c389d2701816494839' 
  AND token = 'ISTBIci0mIPuD3NKGmGGnQuQt6CQryicH458x1bKrjc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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