SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '35bb83ad78df996e6607f3d5fc0c2cc2a468479447b5b106a0355e54e50d558c' 
  AND token = 'cardHQk0sYaq9VHYV92U2XmR3qsbS9dro6HIwUB/deI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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