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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '4c15f34452d876ac12caf4db59dc4dbc824d314515db2b01f57b08a30d9342a5' 
  AND token = 'UDYDo46g11JemrxmnYGEazePHjKrrDi9YTgc08uRM5Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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