SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b877ee51855518fcadc352d5e1f751da65db691db97ca7aa95bc4cd34eb27b40' 
  AND token = 'xEB8wHIScDbfwOop6P4ETojCFB80zH9fBygb0k+JysM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00050

JSON explain

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