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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '3c75d11507d44bcb6cd23fb46ab1106ad3e29212a941e3c37be8acf80599f43e' 
  AND token = 'o2pcYipE/3+lhAPFJ1Xwn8joFd+7CD9o8Gsz8tAc/Kc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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