SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b22dc6ec320dd0c52545caddc9399507d92e7426850a076a3ccb7a7ddfb6f79d' 
  AND token = 's8AfTAQ9UU5Pz9VSM6oA0y82eKTvr7A1JL/TWRgdYMc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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