SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8ff37923e0ada520caf565c908ce2f23a6e41540984beffa1abe63d624567d35' 
  AND token = '83v+rHO0KXZbbEysxOuiUM+k0aYP9os2+30tZas1spI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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