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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'd6b40e64c4af636fed8949ba9e78d857578387eec43b8dc11a6900bc83b2f14f' 
  AND token = 'sxo/Xd/lOoT1uuohjnYEyzNSVZ1cFuG4konGNu8QHTY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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