SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '218b3243ffd6958cc16fa2921b983b606e7c46a026212d0758323a0a649af8d8' 
  AND token = 'uLxl2h0wuAX9ToEdegDtkyzfoJjdAnZ8bJzWlbETYfo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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