SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b75a8e7260fb2e71cd7e08c0facd839ba336991c6fde409404d87e5c0472a5bd' 
  AND token = 'j/PbpCCAWIkxw6Mc3hq5VOXzlQfRHThcZtBVO8cNZOY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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