SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c96261abab55fd3b24b137140ddbf2f7af0d4b6254932214432a8f1d5dfd0581' 
  AND token = 'L/a+wPrziQrP6ad4kJAIjrKgu91hQGwVYPA/cs89/Sw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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