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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7fe3fe5a527b7c575f6c0df02afc2df3c4263e3d1504051bf49ad0c88d52c264' 
  AND token = '1ac/OK50wESai3xAwDg23v7Dtw9fnlqRZJnzwpcMlgg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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