SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b89f656ce674c0c7714b571460f6f59e942b8f4f8f3fda2d9bfe209a3593429c' 
  AND token = 'KinnR8XsD+lpzmXgZ0AgulmJFisi6vH6PGJQziG/BsE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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