SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '3ffbca4bec5cf80d287add506d888d5a4fda4e5f5f250180e69f3941960465bf' 
  AND token = 'UpuJvUFLzqoZIMffkMNE/mJgCPjJ604h4RxOD0KAT4A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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