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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'f09d796ef542db0b7dd9feb883186b3e49ee4b8d0b6024d664d11be7bd6b35a4' 
  AND token = 'SLTVXKB8ypWG8QJOWU+PLp88VO0xRoZlDDZq0P6xkMQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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