SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ada94793e9951fb189effff5bc475e0e660654389540c28eb3e447126b6a644c' 
  AND token = 'kKLP0IKYAhyS+ExrB7yILPCMg0/NNwKhJszySt/JtzM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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