SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b55b262c480e10eb92c350ed0f7329cc9f7c9fe3ede1a6dd25445505c2c89e5c' 
  AND token = 'bEY5AjBBX0hizkurT2X1SFYi3vyA+tJ5MHePHvk1mTE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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