SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b6fc58e12f79b149ed8cb3d6089a653fea5195c3f810211565752874a799cf8' 
  AND token = 'yES8hZQvOCRmXzD5kWEpg+TkMRFu7NiJRZUZYYrbcjQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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