SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'dd0c4995b0f8a26af886a7de07905777231f66f7bb1cb713e25f86170785a017' 
  AND token = '2oiWU+3IRV1ErqLLVCoyPFGzMZWvmqCQw2QpsBmtAkY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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