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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b1a6661dbc6231e0865f82de54f0d4efa9f7f0a28805b19135340609a6bd4950' 
  AND token = 'd4bO6fIPKf64Z6FV4usFYZedrtCOc2u2zVbGbDZl6zI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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