SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '312a6ed15e750e0db614737a9dbb463dfcc1a7f3be4183673c99af2a6d526bf1' 
  AND token = 'bI+wcx+/hJtX0w4bI0EdPoWhfSfmNcMLUnVc3JPJaSY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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