SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6d2ef9dd92a8564809f4c4e807705848a929735782d0352bdf2f1a41e40394ec' 
  AND token = 'b+BNVCc6PedYVkBaSLEOB13RvUbp31Yar30DnQfKpuw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00051

JSON explain

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