SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c73823e1e7ecad251b5bf4fa1d5276cf3e75cc71565e5ab8e0bd6409ad93c03e' 
  AND token = 'mdQKBD+KHzGfpJicpjyzuSw4JpBvZIuDGlUhREIVPnk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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