SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c91061c82f82504e72401962ea72a14443467d4029eb63a06491f5be797d6f93' 
  AND token = 'ydSY/zXI8ZUVISVfwrb4tEm6YjZOW+/qhIm8b7cB8Ew=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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