SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '18759ad9ceffa9e410e811afd503d651691e23644a082f6944a87cf202f35cf7' 
  AND token = '4F7ZhQMBua0CBdrJxg5ppHsziiGajXbikMbaOQ+pUCk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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