SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c842ed541700f9dab12402130be2ce9842759f9b3f3bc65b04de8f8d1c6cff0a' 
  AND token = 'm/Gltf4Widx0ql1bgmE/36sCaNxsKR6cb5JCETaZ+WM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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