SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6e99359fc36f7b077c3762f38e06cfc7fe209cfb342cddeaba98091e8798305f' 
  AND token = 'vnybKdFnCmPbW6YGZFsRu+K+FReD0iKEXv+U2I2KddM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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