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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6c0a6b997994ff77cd43ead6fd1439c4b278fb4fe78730a5e298fe4544da76eb' 
  AND token = '6JOWAnK8dZffFRgMieBr8aMElNOwYCBmj604csCdgr4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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