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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '799c8ce8550f47df69ba9a9673637c4b0bb687cb31940ab8e2251a742eb4dfce' 
  AND token = 'SmTiebvv8Nf7Z+JPxQZzzKOwOhCT5T9I1e8PB8B5dxk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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