SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8b5050224df82b19a9d930e4f9197e175bbb5f1cee9927f3cf289d9d79a59f4c' 
  AND token = '5DZ1DK0wXFz3Psiglp/mLfJQiyI5NHOEqXLsRq6xUjk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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