SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9565759b43e309ae059b60e90c6134591aef39f0cfec9d923d792bd50e89cf30' 
  AND token = '0Mex4R7sPRFReyPTVHcE/3sZFByg6/0otVMIgsAjFvc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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