SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '920241721fbc6c59c119490a470b3f052a2a519baded38a9b9d0bb17b3da4ff8' 
  AND token = 'zaf78gLzxxs6FvPV8mGGgWgmgR+xBgFzK4+XQjUgGs8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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