SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '770276082199c9c041f1869256db2820dce34d2140fb488789420e7967da5358' 
  AND token = 'ThJE7Cs5bYo0rxAomonmYZ8TbAlKs1ApUvqdqu+pJaU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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