SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '91571c0f57b39a92156fbe88dd7c5644b9bbcf2ab9a3e8728dde94f8327c877b' 
  AND token = 'JrC1ExmB87Co/8Sm/pvUXB5+PsY3shSbqd14IImsVqg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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