SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '3154e501f8b311fc9dd58cff408e555decf472fa3484922a27708844c7ee7426' 
  AND token = 'DtTaejTVEkw6vgaDMhkUhRFt3NF671FibzJF99/DNPg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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