SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c52c92f681acd06dced4e001141c43d4dbaf67f79cac478f409de8884fc43668' 
  AND token = '/ZClqKskKYovmTGB08NJztZPn0ffFN99LdrpAYcPZB4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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