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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b255659ef306a0642b2333c4525e4f70eb5ea84ec8d8bfce6f6ddf7cd96fcf75' 
  AND token = 'Q6fRYDqHul6qNfyQoXCmmzr+kxlB819rWNwGUD1iHq8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00047

JSON explain

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