SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '16576ca8fac8be7e71d36112cb052befc8bf1276f46ca46b8eeb92b84465ffc6' 
  AND token = 'YGESxdUcGhoypNDncalsJcJppki8kh/MHSGj8G4C3Eg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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