SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '9642845096003784394fe8317677ad85bc6cad71a96e91a3f0910e53331862e7' 
  AND token = '2hyCMYyJB4Igeak0GsBwdRmNpMjveUV1xazYf9UTm0g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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