SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3ff27f21c90e31155745b5dc1d7f3667c8e0df713b0c7c278f140a7dcc252b81' 
  AND token = '6dy9cAkQZPj3sku75BSRKe1L3NbA5EKpG/m3yp8DWQM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00052

JSON explain

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