SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7eb1f616c8b08754ac2e11dd97da21ccb9542ca52da168123677673ac95e0352' 
  AND token = 'a6qXLTfFvapUKYRCI1JusGZb48k/mjbDo9v4+tDIm54=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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