SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '174cecbc41e77f4d74bd41574d58b373490f300728588b8e0e0c3c123fb159d6' 
  AND token = '/RxJU1eEFTuv+GHex521qz+9vQFgMOZFXnKq/rGh1Ms=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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