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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '18b6beac32a295872d75dfb2435996e977618927c81b6025040da1f9912a48db' 
  AND token = '1gET56htpEG7qXLjO7ymq8kKxXQfsLczUqlzRY6QgD8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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