SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '56d6495b53ce6c73faeb4da3f12999295d674613d242615c1dc691e8a1dcb46b' 
  AND token = 'OiRKxPVRxNODeIEReLtkkwe9ICzhbk4fxFwWEKm0IGU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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