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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '283c8dbedadd850f920611a5cd34f5be2289b6858892a6e8492dba2b6691ecb5' 
  AND token = '3bXYoYvIRliWC7kRa1UuHnymqo+uNX3PL3kNVlg2SXs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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