SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '121d8d025866507c7b99fdbb0643a074e2ead71f8e6f216fb59591204e909d51' 
  AND token = 'Sg95AwJH6Dyqo90fVabXvQl8VBEGc8GzYjoVRiMY+Zs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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