SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a75c6248f93a4e7aefe36ee5896b8f61a0be489d97877b91f26775add2f0e173' 
  AND token = 'KCY/rYp6MIvUMrG3fLZRlIC38BPVbKw4y9NzpfOKnB0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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