SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '0516875d8b84c1abce00923a471420e2603570fc9da1c10f6d9164abd2de1eac' 
  AND token = 'gR6IKuvv0czIHCRpn5McryQiGM4lTQ8maIybfiascTI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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