SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b5a4335d2e54e6a1062a5846fa6380dc70e3fd2afea08d1d831533ba9ae6cdfb' 
  AND token = 'T9Xqz5OwkCWq+JLpIavTIRlwZQqLbje/WVAXiUOBJlY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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