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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21e613b4d9c9ec1969f83a6a50b7dba0f1b6230b900eac61ec8cbb6993655e29' 
  AND token = 'zZs/3dH7ggoYrIAa8DTa3VHXcCrwW0uCj9kV/j+3ahI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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