SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '29c76fdffe183d047809e80cb42a063d461e12d232a1e13024b68472c266058d' 
  AND token = 'mVJvlbHy4QtHv9XdAbiKqlm9vkRY3ksQQmKpxm1yeYo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00047

JSON explain

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