SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6d50a98518295ef888689173c5d112283d157a0ff578ab53e8708fe38b73b49b' 
  AND token = 'IUmpBpBxAGoyVAQPGnyNNTPKZcIcyrlv3eVIAJG+m8A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00055

JSON explain

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