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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6d3a2fe87ff493f5266e80dcbabc8d2cc529e7b3297d8b34e585395f6c4c04f' 
  AND token = 'MQWcrESwQt74uP+tFMXnkwlCo9yTk8eTeEh/hZ2gpyA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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