SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8f6cf098410ebfca579083783c8a6ad664e18a3b67b4e184ee8500006015ce95' 
  AND token = '+O+5ultarPRsevvzj9eKyf0NSKR+rRPOHoyZTKDIvC8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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