SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6b77ad9d6b5b9c932ded8949c92635d0281dad342fda33eb3f7fc49fa69da978' 
  AND token = 'PbfrRLtVvp3ZJLTgQrfTRUOfLsAPiwdlibm/tPjepmw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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