SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a23834ed9a4d536817e934424d2659a8684c7b50f9aa7174d688a25611b64e16' 
  AND token = '7mSia24o12Wx84rqbXiDwKVC3YrBvWKDdXXEoSTZUSg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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