SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b15ed443d947f83191a0c9f72e7394f96493570eb7457329dfeacad48edb39f5' 
  AND token = 'sQWzeiTtlMopn4beKxJT7adWC7rHU0qnsMROetJVqgQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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