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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '28323a70cdf5928dcf1ff4bc734ea57782b99c0f9b64e7a37a4f91f9988634d8' 
  AND token = '6sFeaGQlTvIjsTeTyzfOJk3WDNjCmZ7Ga9pNotuWgOM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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