SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2a73daf2bd218081a5c04c4c626637bbafc6be6011a4b7067ea1230c5d2e6e4f' 
  AND token = 'x3jDBwfbqpZ1ufWnHOJHbVPU2NRgKVpxMhYqLOYQLMY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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