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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c6dcb7250401a8c0ee6fcdde7ed94583d9d372df8fdd1b203dedf30f07a3ddc6' 
  AND token = 'TTGSqgg4TJaSjtJgdmjik/tMQH4LX4ckT6+k/WE1f8M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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