SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b9eb557e50ed81f8c94e9ddf51c9fa82e4f0cbcf26cc050495213a73e336a29c' 
  AND token = 'OSwpGn/GPQseJyovKDDaqYk0ze7Dn85iGjEZhLBuTfs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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