SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b5ca32fe30433158227e7cb58ee6ac3766030755901f40686050ca40130a0c9' 
  AND token = 'nDVzirwc3gWFJpZnbW9pHqMipVdeMpxqGKTNXlB+uW0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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