SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e1212102aac9d615357d200cd6918f0d356d41f6bc4b3c724c162296da6c2a18' 
  AND token = 'RFtMGkXSBZUpZqAa+1BsFff8DA6lCRqzR/ZrE3UaOIw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}