SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c42645b82d11478fdec7458712e5049f9f2532988b3d917f6d2d8399769d44e8' 
  AND token = 'sadIEwRNVNo0rqGLyAtN1cgi7N7zR9tK4OtHHWITDYc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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