SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '646343be37400958e07b2ae270e31da53f0be2227a10e3da4e012603c6bf5456' 
  AND token = 'AVjnHFduxOwi0GOWM1J8D2WUA2kGwpofxlpXnFv3l1U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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