SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dfe1c37b16d050ea1cb795e7f919c87400fcec63df872bdb10f841167e3acba8' 
  AND token = 'EkPoWj+DPrDtnBCWSQm8bFKwjZIzwWk/5B2N/BrB0u4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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