SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '35ac9357a4a0dc1676a3021a3b665c315760127887d3afda5a9ac6f892244437' 
  AND token = 'IguNft4/r0XvFbbrikHbqG0mYWj4+07PLjUv1eBzmYw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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