SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'a2c4f0a95667670429362d0b6b17390947b44856bc687b4a642a615f37f53259' 
  AND token = 'lTV+LEriGcovPvUJe2A82c/BKVNcHi6e3EBuD3FOQYs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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