SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '273065f1dfecc77026f84d9de3b38f455266d1fda8a43ff278d9a8619eed9416' 
  AND token = '252+sFRo791/BwOIVVGvbtilZzNZ1lTu36y3kHSuaqY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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