SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c59f9256e32a4103aef8fe049625378fff397cde2347f83408c96166ac4418ca' 
  AND token = 'HImb7QYHsdboQh3EfOBEqCJBBdzVK/bpK+aTFeGGgeY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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