SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1b78ccfa56a45da483cce36e834d7af61938c05a6f490efb5d4b94e67c550e7f' 
  AND token = 'yV8mU8tUn5+jymH2LBEJ21dlb88ahLKwrkemhByNVQo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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