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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3f331227a72519abf680df6bc99f19f37b03420a2f281d22ff164c8c2c592a28' 
  AND token = 'f4tmvaMhPisjYT7nbNAURKlPLhwVXUyAYygKYdfoOD8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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