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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c457ca0f91b30fe80010ba41ffdde2eab91b84e08d350285bfcb834fa6583309' 
  AND token = '2tZtRsoGfNfww1ULvXIqfRwhN0w3OWygw6wmxiyTP6c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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