SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '557f6b38c7385b4df12e1752563b3fcf23a576ef9f5742764741282265184342' 
  AND token = 'V5BuIklj6v3wxcLllu1EFseXZ6qk5S2XbtA28cnnAoo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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