SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '1bf03c5cd17535870c7297591625c91e21035e96f92aad5ac306572fe60a08c6' 
  AND token = 'RkfAXuTnIAvLybd4f/mdS/tKhNsmOn+SaUAG2bSKvh4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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