SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '29b7846c5116be7953fa578d9dece92452d646d57c46b0833a1431e3c3c29d15' 
  AND token = 'IW+UKkDRRvOFuRKBLrNOTIaeNlwmfPrqUmV2c1Y8Bys=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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