SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '42243e38b87ea48f4371d67ea8e2adbe657f098e9784a4964caf91305aa92a67' 
  AND token = 'WOZTT+JHDXTVu4sZdztUOXvxiNxVaQTwrQ/wBiHvLTw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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