SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '261d994a997d08784af398a239d57af3078d583a85115660481e78207134b00c' 
  AND token = 'JBi7XYIXhjkhWXqbjzBwxPpGN4x8zZaaNvY0bknmSdo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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