SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fc2f578da4f6cacbc7a787f239dd0fb378033c9717d6e5b39513aa06f8075758' 
  AND token = '3OHjkrOe/En/iq60mtwmwI1fOliC+wK0rI88PxlADoI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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