SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '436c81659310de1248f8e20ae35664f0a13f65c19d5fa1bb2d8f74c440a6c879' 
  AND token = 'S3CtTgOqCoYYp/8yhbbCPGBO/kMmwGUqjRVKLTDEbtQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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