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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '4a61be64a46e37a9d1cc13c4ca217523922e58d6946acfbd87bf0a03e7a9ad62' 
  AND token = '+75xGB643lg3wlGCa3I3q+tTfZNJHDi12OzuHRCWFko=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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