SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '35ad2dbf896e54514983565cadfaa06691da194e16995b27fcd5d37d6460dd50' 
  AND token = '9N/TECZcEOrBxwkO/LTzj7pRTjv5RUKDXL5NxcbHgZk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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